WP,
If your decision is going to be based on the fact that you want to fly military jets and you feel you have a real chance in the Pakistani Air Force and little chance in the Royal Air Force, then go for it my boy! You only live once. You can sort the rest of your life out later.
Also, you will probably get the opportunity to fly a greater selection of aircraft and not bound by the OTT Health and Safety rules that now exist in the UK; so you will probably have a lot of fun.
I wish you all the best mate.