When your tradesman has completed the work you will be expected to pay the balance of your account, never pay all the account before he has finished otherwise you will have no power when it comes to sorting out any problems.
Before you hand the final payment over you should check:-
Everything you requested (and everything on your written quote) to be carried out is to your satisfaction.
If you have any guarantees that come with the work (i.e. corgi certificates) you should make sure that you have them, you are entitled to withhold final payment until you have these in your possession.
You have a receipt for the final payment (as well as any other payments) the receipts should say what the payment is for, along with the address of the tradesperson and the trading name.
All rubbish and debris have been cleaned from the site.
You are not entitled to withhold money owed to the tradesperson if he has done everything in his quote simply because you decide you do not like what you have chosen, that is not his fault! Usually the tradesperson reserves his rights on all materials used until his account is fully settled, this basically means he still owns the materials until you have settled the account so he could actually take them back!