List,
The plumbing has held up for the last few days, and I have got a Honeywell wiring centre (pcb type) for the basic heating system, which is wired for a conventional S-plan with a pump over-run.
I have also invested in a large plastic box and some din rail mounted relays to handle the extra pump circuit. I might even have a go at making a dedicated controller from an Arduino - but I am beginning to like the simplicity of relays and pipe-stats.
I found the Honeywell wiring diagrams on the net - and was impressed what they managed to achieve with just a 10 way terminal block - it's justa shame that the bloke that installed my controls failed completely to follow any Honeywell wiring scheme

I have a 1.75kW dedicated heat leak radiator, and if this cannot handle the full load, the extra will go to the hot water cylinder and then the rest of the household radiators.
As we are now at October 1st - and in "my book" officially into the heating season, I am looking forward to the first firing this weekend.
Ken