I'm having gas central heating installed in my eight year old semi this week and would like some feedback on is weather compensation a worthwhile thing to bother with or is it really just another layer of complexity that may go wrong and deliver little in the way of real savings? Many thanks, Richard

Weather compensation is pretty simple generally a microcontroller with one or two temperature sensors. Savings depend on the boiler, the building and heating system design. For my (9 year old Vaillant 24 kW combi) boiler:

Heating efficiency at nominal heating capacity (18.9 kW output) and 80°C flow / 60°C return: 88.4%
Heating efficiency at 30% of nominal heating capacity (6.2 kW output) and 30°C return temperature: 97.7%

I designed the rads and UFH so that the max flow temp is 45°C

If you don't go for weather compensation, then just upsize your emitters so that you can set a permanently lower heating system temperature. That way it'll also work better with that £1000 heatpump that you'll hopefully be able to buy when the boiler kicks the bucket in 10 years time...