I'll give you my opinion. Tire fitters do an average job of fitting the right tire without damaging my wheels, and quickfit service centres do an average job of putting the correct oil in my car provided I give them the correct oil and show them where it goes.
Would I let them loose on my car armed with a laptop and enough software to change essential engine management parameters? Errrmmm... No.
If I was going to have a remap done, I'd go to someone who does it for a living, not some place who just bought a franchise and wants to make a few quid selling generic software maps.
£235 is cheap though, and if my local service place started doing it I'd probably be asking some probing questions to see what they knew, just for a laugh.