Guidance notes

Once you have agreed for a tradesman to do work on your property, a contract has been made between you and the tradesman, so before you agree to any work, obtain a written estimate/quotation which details all aspects of the work to be carried out.

Estimate or Quotation?

Be aware that there is a difference between and estimate and a quotation

An estimate can go up or down but should not change greatly from the original price.
A quotation is a fixed price for an agreed job and cannot change at all.

Basic Rights

The supply of goods and services Act 1982 states that when work is carried out by a tradesman, you can expect it to be done:

With reasonable care and skill - Work must be carried out properly and to a satisfactory standard.
In a reasonable time - Work should not take an excessive amount of time and a time period should be set in advance of the work commencing.
For a reasonable charge - The tradesman must not charge an excessive amount for the work done. If a fixed price is agreed, the tradesman cannot charge more than that price and the customer cannot complain that they could have paid less elsewhere.

When the work carried out does not meet any of the above rules:

If the fault is due to poor quality of work or fitting and can easily be put right, an offer of repair would be reasonable.
If the tradesman cannot repair the fault properly, then you maybe entitled to compensation. This could be the cost of getting somebody else to do the repair.
If the work takes longer than agreed, or more than a reasonable time, you maybe entitled to compensation. This could be the cost of getting somebody else to complete the job or a sum of money for the inconvenience caused.

If tradesmen carry out extra work without the permission of the customer, they do not have to accept it. The customer can either:

Accept the extra work was necessary and the extra cost reasonable
Ask to remove or undo the extra work where possible
Negotiate a reasonable price or acceptable solution.

This is not an authorative interpretation of the law and is only intended for guidance.