hate to say this but the reason you're NOT getting any compensation is precisely because you DID NOT stand up to them.
I got a phone call yesterday saying they were changing our accommodation to apartments 6kms away from the Bellevue. They offered us no compensation, no apology-nothing. I returned their call after viewing the apartments over the net and told them I wasn't accepting the apartments. They offered me other apartments in Palma Nova which looked better so I settled for them.
When you settled for the alternate apartment that was the deal done. You should have first asked what compensation applies IN ADDITION to accepting the change.
When you accepted the change you presumably were as happy as was reasonable giventhe circumstances.
Then, as you state:
In the meantime I was talking to a girl who was in the exact same situation but had been offered £40 compensation for herself and her boyfriend
Bit late. Each claim will be treated individually so you cannot compare the two situations.
I do feel for you, not too much for the loss of the possible £40 compensation but for the fact that you have not got the original apartment that you wanted, booked and paid for.
You don't say why D.H. moved you in the first instance.
The only lesson from this is check your rights BEFORE accepting any offer from a travel company. A post on this site beforehand would have possibly helped you.
I doubt you'll get anywhere now lodging a complaint other than wasting money on postage.
Sorry,
Mike