I have been trying to obtain some of these for some time without success but have found a company who can supply solid copper ones which are apparently used on aircraft. They cost 25p each and there is a minimum carge of only £5 plus post plus VAT. The supplier is LAS Aerospace Ltd on 01837 658081 or www.lasaero.com.
Maybe that will be of use to others and, needless to say, I have no connection with the company except as a satisfied customer.
Regards
Brian Hutchings

Brian.
Paul Beck (www.vintagecarparts.co.uk) and Complete Automobilist (www.completeautomobilist.com) both list these for 24 pence - and you don't have to buy 5 quids worth.

Charles

Thanks for that Charles, I have now managed to find the Paul Beck ones although it does not come up on a search for spark plug washers. The Completeautomobilist site is being altered and very little seems to show at the moment.
Regards
Brian Hutchings

They're here:

http://www.completeautomobilist.co.uk/search.php?search=spark+plug

Charles