The two strongest airlines without a shadow of a doubt up here are Jet2 and Thomson. Together they have made massive investment in NCL, supporting the local economy and alike. You can't possibly say that RYR ops, in from foreign bases, with foreign crews and frames is going to contribute positively to the local economy. It isn't. As to whether it will drive away the airlines - maybe a 1 frame reduction from TCX, and EZY shutting shop. TOM and LS are strong enough to fight this out. At the end of the day, passengers do have loyalty to airlines, of which is earned from positive experiences, good flight times, and friendly customer service.
All the major high streets/shopping centers still have travel agents, something which is clearly still the most popular method of booking with our demographic. Hays and Dawsons both have bonds with Jet2holidays, and have more money to make from this as opposed to selling everything separately. We aren't London. Most travelers aren't business; instead off on their annual summer weeks in the sun. Our TAs aren't going to support RYR like they do TOM and LS, and people certainly aren't going to adapt well to having foreign crews. Attacking routes that are already well served won't go down well at all (and don't quote me on BHX - its a big jump, and I'm sceptical of its success).