Are UK summer acting/musical programs worth it?

Hello!
I'm a 20 y/o male who is beginning an opera/musical major here in Central Europe where I've been for a while. I've been considering eventually trying to move over to the UK to try pursue musicals and acting after my major (I'm very intrigued by the culture and English is my native language).
I was thinking to try to get into a summer acting/musical program in order to gain experience and insight into the UK system. I've looked at some summer programs such as Guildhall courses, Royal School of Speech and Drama courses, Mountview courses, etc.
These courses are quite expensive, so I’d like to ask—does anyone know if they’re known to be beneficial, and in your opinion, are they worth the money?
(I know it's bold of me to assume I would get accepted to them, but I just want to be sure about them before agreeing to commit myself.)
Thank you for taking the time to read my post!

It depends what you want from these courses. A general acting course over the summer is a good taster of what drama school is like at that school. By its short timescale, it is not going to give you depth of training. The more targeted ones (Meisner, Stanislavski etc) may provide a little more training. Some are for working actors and you will need to evidence this.
If it is a precursor for applying to drama school, it is very useful before you commit £10,000s and years. The short courses are not usually entry by audition, so if you can pay then it's fine (usually up front).
Getting into the actual actor training (BA or MA) is very challenging but auditions are held worldwide, so quite accessible in that respect. To give you an idea of how competitive, the approximate acceptance rate for Oxford University is 17.5%, Cambridge University is 23%, Harvard is 4%. The drama schools you have mentioned have an acceptance rate of 0.6%-0.8%.
If you are already training, you might find it 'easier' to get an agent and some credits in your home country prior to travelling to the UK, which is a very saturated market, because that will give people the opportunity to see your work and give you credibility.
Good luck!

Thank you very much for the information and advice.
Do you happen to know anything specifically about the Guildford summer courses?

Basically, I'm having a hard time deciding if I should attend the course. I'm wondering if it would be better to attend a course in my country instead.
Would attending the Guildford course look good on a CV or would it really only be worth it for the training itself? I thought that attending the course would maybe help me make connections in the UK for the future, but I'm not sure if it really works that way.

I understand, it's difficult to know what to do for the best. What I am going to say is based in what I have learnt about the industry and how things work in the 'real world' but some of it is my opinion so keep that in mind. You need to make a list of pros and cons that will help you decide. I will try to address your points and ask you a few questions to help you consider this.
You are absolutely right about wanting to make connections. This is important for all industries and especially pertinent for this one. Your cohort play an important part in that as you share opportunities with each other as they cross your path. So, it's important to understand who will be on these courses.
A course aimed at people interested in exploring Acting will be very different to one on a specific technique (e.g. Meisner or Stanislavski). The former will have people wanting to understand if Acting is for them but most are unlikely to pursue actor training (getting into drama school is very competitive). The latter will most likely have people who might be working or already on another course (e.g. Drama degree instead of Acting) and these are the people you want to connect with. However, some of these courses are aimed at professional actors and you have to prove you are working, so might not be accessible to you yet.
It is a reality that the reputation of the drama school carries a lot of weight in a CV. I am not saying this is fair but that is how it is. Most reputable drama schools in the UK, of which we have many, offer great teaching and the same teachers move from one school to another. Plus, anyone who has got into one of these drama schools is talented. However, having RADA or LAMDA carries a lot more weight in Acting; Mountview for MT and Royal College of Music or Guildhall for Music. So, consider that when making a choice.
Also, doing a longer course at these places gives you the prestige on your CV and the network (staff and other students who have time to become your friends). Perhaps a more substantial course after you have finished your singing/opera degree? Would your money be better spent on something that has the potential to move your career forward and complement your current course? BTW, you mentioned Guildhall before and then Guildford, they are very different. Guildhall is considered way more prestigious in the UK and internationally than Guildford.
Also, expense. Short term lets in a student hall in London will cost £300-£500 per week, which is in addition to food and the course fee.
Are you training in just opera singing or MT? If you are only doing opera and you want to do MT, you might want to take regular dancing lessons. Even the new people you will be auditioning against in London would have come out of 3+ years of training in singing, dancing and acting. They will also have agents (even more difficult than getting into drama school!), otherwise you can't get an audition.
I hope this helps you with your decision. Last thought I'll leave you with: your career is a marathon and not a sprint. Is a 2 week Introduction to Acting at Guildford now going to look good or is it better to have 2 week Stanislavski Technique at RADA towards the end of your current course as you are about to launch into the industry?
Good luck!