I thought I'd heard that as part of the seedcorn "deal" the individuals had to fulfill a minimum return of service, several years, in the RAF after their return to UK. This was a measure put in place in order to prevent them jumping ship as F84 is suggesting they do.
However, perhaps I was misinformed, or if seedcorn is extended perhaps this requirement will be dropped, on the grounds it is no longer realistic, I believe one of the guys was 47/48 when he went!