I have experience with Royal Holloway, not Psychology PG but I did take a few psychology modules at UG and then a MA in a different department. I think the atmosphere at the uni is very friendly, there's lots of support if it's needed, the accommodation is much cheaper than the other unis you mentioned as it's out of the way - but some may see that as a negative. Whilst it is a University of London college, the train from Egham to London Waterloo is a little lengthy (around an hour I'd say but I'm not 100% on that). The train station is about a 15 minute walk from the main uni campus. I feel like the library facilities when I were there were brilliant (you have Bedford which is more modern and Founders which is just like a library you'd see in Harry Potter). They have since built a huge library though which I haven't experienced but I can only see it as a positive! It's a lovely walk through Saville Gardens to Windsor, however I'd say Egham itself doesn't have much to offer, adding to that 'campus feel'. Reputation wise I would list it higher than the other unis you mentioned but I suppose I'm biased haha! Psychology wise, just from my minimal experience, I found the majority of teaching was delivered through lectures. The lecturers were very clear and engaging, and even when they weren't the hand outs they produced were. You were made to feel like if you're genuinely interested in your subject matter then have time to focus on that as well as the key theory which I thought was fantastic.
If you'd like to know anything more specific please do ask! Sorry I couldn't help with anything more Psychology specific.