Remember that if you invite them round for a sales pitch and sign a contract you don't get the cooling off period that you would if would from a "cold called" or doorstep sale.
Yes you do - the law changed in 2008. It no longer matters if the trader cold called or was invited by the home owner. Whether somebody has a 7 day cooling off period depends on where the contract is concluded.
If the contract is concluded at
your home (or
your place of work) you
do get a statutory 7 day cooling off period.
If a trader visits your home (invited or not), measures up and later sends a quote in the post/email/telephone, you
don't get a statutory 7 day cooling off period.
It is important to remember that the trader
must give you a written notice of your right to cancel
at the time the contract is concluded. If they don't, the contract is deemed to be 'unenforceable' in the eyes of the law.