stick with the wb 5 year warranty can't go wrong not as good as a cdi but don't cost as much either. As they say on there boilers corgi domestic heating product of the year second year running
only do install so don't know about service but if it is that expensive stick it on a contract. The boilers are very reliable in my own experiance and the price looks very good.
Installed a 440 2 weeks ago amazing performance good to fit considering size first one I have fitted. I recommend a 42cdi but the difference in flow rate is noticable true two tap operation as long as you have the mains
better of to contract direct if you can more money less sh** ,you have more control and can build your own reputation rather than working for orions they used to supply the sparks.