advice pls. Does one have to pay someone if nothing was signed and I don't want them to do the work?

[ohmeohmy]

Paid someone £800 to write a grant proposal which they submitted with little consultation so not happy with proposal but got the money and happy to have it.
Within the proposal the grant writer added £1500 for 'ongoing training' which is neither needed nor wanted and given the terrible history of the relationship a giant stress.

He is demanding payment (in angry manner). Do I have to pay up?

You may not want or need the ongoing training but, as it formed part of your proposal, I presume whoever gave you the grant is expecting you to spend some of it on this training. However, you are free to purchase the training from any vendor you choose unless the terms of the grant stipulate that you have to buy it from the person wrote the proposal.

I cannot see any reason you have to pay on the facts you have posted. However, you say "if nothing was signed" in the thread title. Did you agree to pay £1500 for ongoing training verbally? A verbal contract is, in theory, as binding as a written one. In practise, of course, verbal contracts are harder to enforce.