lindyloo, you don't have to start off getting adversarial about this.
The main difficulty you face is in retaining payment - you're not entitled to do this without his consent, and he would be entitled to apply to court to force you to pay the agreed amount.
If the fee is unreasonable then this is a different matter, and if he disputes this then you would have to apply to court yourself (or submit a counter-claim if he applied first). Your claim would be on the basis that the charge is in breach of the provisions of the Supply of Goods and Services Act 1982 (
click here for consumer information), which, in summary, says:
The Supply of Goods and Services Act 1982 requires a supplier of a service acting in the course of business in England, Wales and Northern Ireland to carry out that service with reasonable care and skill and, unless agreed to the contrary, within a reasonable time and make no more than a reasonable charge.
The issue of the charge having to be reasonable is an implied term of your contract with the tradesman. Where the charge is before carrying out the work, as in your case, then the following provision applies:
In the Supply of Goods and Services Act 1982 said:
An express term does not negative a term implied by this Part of this Act unless inconsistent with it.
This means that you have redress if the tradesman dupes you into agreeing to an unreasonable charge.
So, that's the legal situation, but I guess you want to resolve this without going to court. So, write a letter to the tradesman and either post or hand it to him. Explain that you are concerned that the price of the work isn't reasonable, and that you are offering <
insert there the sum of money that you think it right> in full settlement. If his English is poor then he can take this letter away and have it translated/explained to him.
Pragmatically, it's still better to withhold payment than risk the uncertainty of relying on a court order to obtain compensation. There are many cases where the tradesman will give up
because he's unscrupulous and would rather vanish into the night than appear in court.
However, I would reiterate the need to stay calm, polite, civil, reasonable, and yet strong in your resolve. Remember, the law is on your side, so you don't have to get angry or recriminatory with your plasterer.
____________________
Moving on to some of the "advice" you've been given so far...
breezer said:
lindyloo said:
pay up but tell him I'm going to complain to trading standards.
on what grounds?
Is that the best you can offer? It's blindingly obvious that the lady can complain on the grounds that she believes the charge to have been unreasonable.
lindyloo said:
...........after all, I agreed the price..........
Sorry says it all really, chalk it up to experiance
Even if you could spell it, this wouldn't be a helpful suggestion.
lindyloo said:
It was only a verbal agreement, though.
breezer said:
Still legal
out of court too.
you agreed the price before work started.
That isn't one of the situations where the express term overrides the implied term.
joe-90's advice here is generally good, although maybe a weeny bit aggressive on charges and timescales, but I don't believe this point:
Last case I heard like this, the person contacted the Police for advice. The police told the rogue trader that they would investigate his business finances - he dropped it like a hot potato.
This sounds very much like an urban myth - the police have no power to investigate finances, unless there is suspected fraud, and have no power in any peaceful civil dispute involving money.
and you ARE in London 
....now ca$h jobs are around £120 a day here in the stix.so I`m told....therefore London must be £200 a day for cash and more for a company with overheads........and that must vary in different parts of London
