The difficulty with those types of virtual airline arrangements is that the UK CAA is completely allergic to them. Even the regulatory provision which allowed Manx2 then Citywing to exist has been closed off for all but the most infrequent flights. There is a resurgence of them in Sweden after the failure of FlygBRA but between a combination of airline operating licences, ATOL licences and the lack of traffic rights for non-UK carriers past the Brexit transition period, it's as certain as it can be that this type of structure will not appear in the UK (or Crown Dependencies either). You'd be into getting a full AOC and Operating Licence.