In the meantime looks like everyone’s gone to bed - need a parts list at a minimum for my wiring setup.
All you need is a standard 3port spring return valve(honeywell best, followed prob by ACL/Drayton, take your pic with the cheapos) and a bog standard wiring centre. However a warning, lots of trades people like to fit and supply and are not all that keen on "labour only jobs" for whatever reasons
Also you will need a new wire from your programmer to the new wiring centre in the airing cupboard(this bit at least you can do yourself to save labour costs)