I'm not sure what the cost of your holiday has to do with it. It makes no difference what the holiday cost.

You will stand nowhere until you have written at least twice in an effort to settle this yourself.

I'm not really sure what you want from them?

£189 for an upgrade is cheap, and don't forget a chunk of that is tax. If IFE not working was the main complaint I can't see that offering a refund of 25% of the actual upgrade cost is a bad offer. Failing that I suppose they could have always delayed the flight for hours, and waited for an aircraft where all the IFE screens were working?

krazykev i am not sure where you stand but i understand your frustration £189 for a poor service is £189 wasted.
was it a 767 you flew on ?
i flew last year premium to Dominican Republic, entertainment system kept crashing for some people onboard but not others, luckily ours was working ok. we didnt get the drinks before flying on the return flight but wasnt too bothered to be honest but some people on board did complain.
just got back from Jamaica and paid a whole lot more to upgrade to premium, once again the entertainment system didnt work for all of us this time, its a long flight and anything to help pass the time would have been appreciated, premium seats they say get a dedicated cabin crew, i didnt find them very dedicated to their job!,they served the meals etc did the basics, one man complained to the stewardess about the entertainment system not working (i know it wasnt the crews fault) she snapped at him he wasnt in a cinema, he made it clear he didnt pay cinema prices. the stewardess was raising her voice more and more.
until another stewardess intervened, i wouldnt expect to be spoken to by a stewardess in that manner.
only drinks we got apart from tea at meal times were 2 cans of lager, we asked for another can about 7 hours into the flight . am still waiting for it now,
return flight crew were much more pleasant, but again we asked for a lager mid atlantic only to be told they didnt have any onboard, they said all had been used up on the outbound flight.
very disappointed with the premium service delivered by Thomson, i considered it a waste of money .

Was the holiday itself ok ? Presumably that was what in the main cost you thousands and thousands ? If you feel that £30 per person is not enough comp for no IFE maybe in your second letter you should tell them how much you think is a fair amount ?

Were you actually in the premium cabin, ie with the larger seat pitch, ability to select your seats etc presumably that is a large part if the £189? If not and you were in standard, then they will normally refund the whole £189 if that cabin was withdrawn for any reason.