I know nothing about your car but…
I fully understand keeping a car for as long as possible, I buy a car about 3-4 years old and keep it until it dies doing a basic service every 6K or so.
The Dealers get a premium payment because their stamp gives extra value to your car and stops any argument over a warranty (I know in theory you can get your car serviced anywhere and it’s still in warranty if the service intervals are met, excluding probably bodywork), I’d never use one once out of the warranty period. A garage stamp just shows regular intent to have the car serviced and I don’t actually know of anyone that checks the reputation of the garage that has stamped the logbook. I know of one fella took his car to a place regular as clockwork and everything was stamped as should be. I took a look under the bonnet after an emission fail on the MOT to find the airfilter was black and ripped through and the oil filter was rusted in place – mechanic had just been stamping the book and taking the cash. A basic service and the car passed the re-test.
For you, you want a regular car working well at a sensible price, which means a specialist/good local garage.
For me, I got into doing a basic service on a regular basis, it takes less than 90 mins to flush the old oil properly and drain from the sump (as opposed to sucked out by a garage from the dipstick), swop out the air, oil and fuel filter and bleed brakes/do pads if required. And this is without a garage on the side of the road, total cost is less than 100 yoyos, although I have probably spent 100 on the bits of equipment that have lasted me over 10 years so far (jack, axle stands, chain whip, 36mm hex and socket wrench, large box to carry it all in).
For the big stuff that I can’t do on the side of the road I go back to the good local place and get them to do whatever work is required (ie second wheel bearing because the first was a right bugger and I couldn’t be arsed going through all the buggering about again).
If you have a good deal from the dealer for this major service (timing belt/chain/tensioners included?) I’d probably go down this route as a final “treat” for the car and then chat to mates and stuff getting recommendations for a good place to take the car in the future.