> What is the UK numbering for a 5Z3 rectifier valve?
5Z3 is a chinese rectifier most close to a 5U4. A lot of possible substitutions exist, my personal preference for lower current duties tends to be the Mullard GZ32.
You can get Valve Data from www.duncanamps.com -> TDSL and get equivalents and near equivalents listed.
> Also where can I get one at a reasonable price? eBay want £10 plus postage.