(2-part post):
You've not stated why the salesman called. If it was a 'cold call' (or a visit following on from a 'cold call' by phone), and if the value of the goods ordered was over �35, then you do, indeed, have a 7 day cooling off period. (This would normally mean 7 days from signing the contract, or otherwise agreeing to the sale. However, if you signed a contract 7 days prior to a bank holiday and were therefore unable to contact the company until after the elapse of 8 days from signing, it's likely that a court would take the view that you were still entitled to cancel).
Where a sale (with a value exceeding �35) is agreed as the result of a 'cold call', the salesman commits a criminal offence if he fails to advise the purchaser of his right to cancel the agreement within 7 days.
The relevant legislation is embodied in three separate sets of regulations which are collectively known as The Doorstep Selling Regulations:
http://www.dti.gov.uk/ccp/topics1/facts/doorst ep.htm
Everything above relates to 'cold calling', either on your doorstep or by initial phone contact. If, however, you invited a salesman to call (e.g. through making a telephone enquiry about a product) then there is NO cooling off period and any contract, in relation to the sale of goods or services, becomes fully binding from the moment that it is signed.