What has really happened and who's responsibility ?

[Gilly]

Advice urgently required please.
A legitimate gas/plumbing engineer is employed to remove an old combi boiler in a one bed house.The replacement boiler is a Baxi Platinum 28kw.
Also in situ is an electric shower (over the bath) working perfectly.
Apparently when finishing off and 'filling up' the electric shower gets damaged.
I am told that the header tank to mains pressure is greater and thats whats caused the shower to pop and is unrepairable.
Now what should happen ?

 

[PlumbBobBob]

you've already posted this enquiry on the main forum, no need to post here as well. thread closed.