Will a non-law degree put me at a disadvantage when becoming a barrister?

You should do the one that interests you the most, and which you think you have the best chance of obtaining a high degree classification in (minimum of a 2:1, but preferably a First). It has already been said, but statistically there is no difference at all between doing a law degree and a non-law degree, so the correct answer is to do the course that best suits you.
For context, I did a law degree, and I shouldn't have. I didn't enjoy it, wasn't particularly suited to it until my third year when I started to get into the rhythm of it a bit more, and had other subjects that I had more of an interest in and should have studied instead. In the end it hasn't stopped me from becoming and enjoying a successful career as a barrister, but it may well have done. I studied law because at the time I simply assumed that I had to do that to become a barrister, but again, that wasn't right. Choosing a non-law degree is not only something that doesn't harm your prospects of becoming a barrister statistically, but from a personal and academic development standpoint it may well be better, if you go on to do well in your degree and are then better prepared for the PGDL and Bar course as a result.

I am glad that I studied history at university but, if I was going around again, I would aim to do a senior status law degree in two years after my first degree in place of the one year diploma (if I could fund the extra year).
After many years in practice, I have become enough of a lawyer to teach on law degree courses without possessing a law degree; but in my early years as a barrister my legal knowledge was a bit thin in places.
This is why I encourage those taking the PGDL to read beyond the course.

Thank you! I was also wondering to what extent doing a pgdl instead of a law degree will impact my knowledge of law as in comparison to a law degree? And what exactly do you mean by reading beyond the course? Can you give examples please?

Read about legal subjects not included in the PGDL course, for example jurisprudence, human rights, company law, employment law, conflict of laws, and so on.

I want to become a barrister, and now I am considering what university degree to apply for. I am choosing between a law or geography degree.
Which one should I do, and will doing geography put me at a disadvantage/less favourable position???

Read about legal subjects not included in the PGDL course, for example jurisprudence, human rights, company law, employment law, conflict of laws, and so on.

I would also suggest, if you want to do civil law, unjust enrichment and claims in restitution - even on the LLB they canter through it very quickly. Nothing to add on the main question though - there is no meaningful difference to your prospects of obtaining pupillage.

I am glad that I studied history at university but, if I was going around again, I would aim to do a senior status law degree in two years after my first degree in place of the one year diploma (if I could fund the extra year).
After many years in practice, I have become enough of a lawyer to teach on law degree courses without possessing a law degree; but in my early years as a barrister my legal knowledge was a bit thin in places.
This is why I encourage those taking the PGDL to read beyond the course.