Hi,
Hope this is posted in the right place...

I have been offered a scholarship at Uni A which covers fees and offers a stipend equivalent to research council level. Obviously, I am pleased but I am still waiting to hear from Uni B where there is a fantastic supervisor that it would be a dream to study with. I shan't hear from Uni B for about two weeks and I have to make a decision on Uni A within the week and I have to sign papers saying that I've accepted. Is it ok for me to accept and, if Uni B comes up with funding, decline Uni A in a couple of weeks?

Ideally, I'd ask Uni B what my chances are but I know that the people I need to talk to are out of the office on leave and aren't due back until after my decision is due at Uni A.

Ethically, I really hate messing people about so I feel awkward and uncomfortable about this but I also know that I need to look out for what's best for me. Any advice would be greatly appreciated.

I would go for Uni A.
Going by statistics, lightning rarely strikes twice. One has to be extremely lucky to have two PhD offers. It's quite rare.

I was in a very similar situation. I applied to two universities at the same time. Got an offer from the first university and accepted as I hadn't heard from the second. I ended up being offered a fully funded PhD from both and ended up accepting the 2nd as the supervisor is highly regarded and the subject area was much more interesting to me. It was horrible having to withdraw from the 1st one but I had to think about what programme was best for me. I got a kind but short response back from the 1st university wishing me all the best and that was that. It's not nice to do and I did feel guilty but as you mentioned you do need to do what's right for you.

Good luck with your decision
A