Holiday Changes

Westin

Red Sea Holidays have chartered Enter Air for their own flying programme to Egypt and then have been using other third party flying (TUI Airways) to supplement this.  In fact Red Sea Holidays with their new Enter Air flying were the first tour operator to announce return of flights to Sharm el-Sheikh after the U.K. flying restrictions were lifted a few months ago.  

Their focus will be on filling their charter flying programme commitments, perhaps only taking small allocations on third party flying. Once those third party flight seats go I suspect they encourage people to fly on their Enter Air charter. In addition possibly TUI are restricting flight only sales on their own flights as TUI would ideally like to sell packages rather than flight only.

If this was a confirmed holiday booking and it was just flights as TBC on your holiday confirmation, then I personally think Red Sea Holidays are on dodgy ground asking you to either change departure airport from London LGW to Manchester, or pay a hefty extra flight supplement.  If however this was only an Advance Registration request and not a confirmed booking then I think they can present new options and pricing to you but on the provision that if you don’t want the alternative then they refund the advance registration deposit.

A read through of these might help you
http://www.redseaholidays.co.uk/termsandconditions

Have you looked at TUI to see if they have an alternative that you like - matched with the Friday Gatwick flight that you want? If so it might be an idea to get the refund from Red Sea and book something with TUI (who have a sale on at the moment).

cc65

It was a confirmed booking, have a confirmed invoice email and tui don’t do the accommodation we want. 

Westin

In which case I would read and go armed with their own terms and conditions and push them for a better resolution.  A good read of the Package Travel and Link Travel Regulations 2018 might also make your weekend reading list.
https://www.legislation.gov.uk/ukdsi/2018/9780111168479/contents
I think they are being very naughty asking you for additional money for the Friday Gatwick flight you booked and that they confirmed. Good luck.