After WW2 the War Graves commission moved a lot of bodies from scattered locations across the UK to be reburied. There were two reasons 1. To make the tending of the graves easier for the Commission. 2. To move the graves closer to where their families lived, to make it easier for their loved ones to visit. Many graves were moved in "batches" that led to these groupings in churchyards. These would have been servicemen and women who had died from accidents or of their wounds in hospital or aircrew who had crashed in the UK or seamen who had been washed ashore.
In general, British servicemen who died abroad in both World Wars were buried abroad - "There is a corner of a foreign field... " - again, the bodies were gathered together by the War Graves Commission and reburied in large cemeteries to make tending them easier.
It was only in more recent wars, where there was a real danger of the graves being desecrated after our troops had left, that the MOD began shipping bodies home for burial. Although a lot of British families chose to have their loved ones buried in the Falkland Islands after the conflict there.