https://www.caa.co.uk/General-aviati...ctory-flights/
Cost Sharing Legality Bit:
The requirement for those costs to be shared equally has been removed. How much each individual person pays is not prescribed, but the pilot must pay something.
Advertising of flight bit:
A flight can now be advertised in advance, but it should be made clear that it is a cost sharing flight, and not commercial air transport under an Air Operator’s Certificate (AOC), since it is an offence to advertise the sale of a public or commercial air transport flight without being in possession of an AOC.
BUT something to note about the "cost"
Direct costs include fuel, airfield charges and any aircraft rental fee. Any other costs not directly related to the flight, for example the annual cost of keeping, maintaining and operating an aircraft, cannot be shared and no profit can be made.
So basically - you just need to setup a company, and rent your aircraft to yourself for whatever you deem appropriate to go around this bit of legislation... Its not rocket science!