"The best performing pension could produce more than three times more pension income than the worst performing one. The really bad news is that your pension fund is more likely to be amongst the bad than the good" The Observer
Depending how long you have been living abroad it may still be possible to make last minute lump sum payments to an existing pension scheme or to top up your entitlement to state benefits.
Whether this would be advisable depends on your individual circumstances and requirements. In any event you should investigate the advantages and disadvantages for each of your pension arrangements of many different options: leave them where they are, transfer them into one easy-to-watch pension fund in the UK, transfer them to your new country of residence or to some other country where the tax treatment of the pension is more favourable.
So many questions...