Looked at the site mentioned,nothing to leave home for,the 37cdi is about £ 7 cheaper than my merchants and my merchants are cheaper for glowworms,Aristons and Alpha,s,Valliant some models bit cheaper,some bit more,will stick with local supplier,any problems,sorted straight away,if you have to worry about £10-£15 on boiler change,something wrong
Also if you are picking up from plumb center,any thing you save will be lost on any extra bits you buy there
Off subject slightly,but hate plumb center home brand stuff