Start fighting this in England. The assholes who are building will eventually try to sell to British people, and you have a case against the people who will attempt to buy, and in that situation it will be a British versus British case. If the developers have agents in the UK then you can issue an injunction against them to prevent them selling in the UK ANY of the apartments they will build on your land in Cyprus.
You need a a lawyer with imagination to do this, and I stopped practicing a long time ago. It will be interesting from a legal point of view to proceed against all possible buyers of property built on your land. Under EU rules the British courts are obliged to recognise official RoC property deeds and other official documents that are properly apostiled and legalised. And by seeking an injunction you are not asking the British court to deal with the substance of your title, just to stop other British people from buying what is yours.
The mere start of proceedings is enough to cause the sellers a big headache and you make it known that buyers are dealing in stolen land, they will be committing a civil wrong against you. That ruins business for the thieves.
The property commission is a fraud. They will offer you something like 100 GBP per donum for land that is worth a hundred times that. And everything takes time which is another way for buraucracies to crush the individual. They live forever and people do not. The ECHR also takes time and to reach them you must exhaust local remedies.
Go for it! Find a law professor who has imagination, and not just a local hack lawyer who deals with humdrum cases.