Are you an MEU1 holder currently? If you qualify, it is recommended that you proceed to obtain your MEU3.
The MEU3 will give you access, if eligible, to social insurance welfare benefits as if you were a Cypriot. As none of us know what is around the corner, the British High Commission recommend that if you have 5 years residency, you apply for your MEU3.
Also, once you are an MEU3 holder, you can register immediately for GESY. If you are an MEU1 holder, then unless you are an S1 holder/receive your state pension, or pay voluntary contributions for GESY, you will be unable to register for GESY.
