"This has been agreed with the CAA due the close proximity of the two airports" - this is not true. An agreement is in place only when it is in the jet2 Ops Manual, FTL section. If you report direct to your alternate base before then, you are operating illegally.
The furthest split so far agreed is GLA/EDI, 48 miles (1hr 3min).
LHR/LGW is 43 miles (54min).
MAN/BLK is 57 miles (1.25) and CAA agreement is far from a foregone conclusion.
You should live within 90 minutes of your alternate base, and guidelines suggest that agreement to dual-basing should be voluntary.
Clerical error? Or testing the water?