In my experience postal votes arrive here too late for us to get them back. We now have a proxy vote that works very well. If you have any contacts in uk it is easy to set up.
If you don’t have anybody you can call on in UK, ask the political party of your choice in your voting area if they will set one up for you. (They identify one of their number who will vote for you).
Alternatively, if you want to vote for a sitting MP in the area your vote will be, you can write to them for assistance with proxy voting.
Once it is set up you just have to renew it from time to time. The Council holds the details of your proxy voter.
Good luck.
Jo