Would anybody be able to suggest a good hire car company at Heathrow and if so did they find it any cheaper using eithe a U.K. or CDN Visa card.

Many thanks.

I usually hire rental cars in the UK via a broker, ‘Auto-Europe’ which compares rates from companies such as Europcar/Alamo/Budget/Sixt/Hertz etc. as I’ve usually found it much cheaper than going directly to the car rental companies own websites.
Do look though at their US, Canadian UK websites (you can choose the country at the top of the page) as sometimes the rates differ (notwithstanding the exchange rate):

www.autoeurope.com

Do you have an American Express card? I usually pay a fee of $25 per year so I can waive the CDW insurance from the car rental company. It will give coverage for up to 40 days a time, no matter how often one hires a car per year. I don’t know if any other credit card companies offer a similar scheme, it might be worth checking with your card issuer.