LOL! I go off shooting for the weekend and I missed all the fun! <sarcasm>
Look, 10 years ago the same argument was made here in the US: "How about paying a gunsmith a working wage?" and "Don't leave the local gunsmith hung out to dry by buying pre-fit barrels. Besides, they're not 'hand fitted' so must be less desirable". It's all bull****.
1. Most rifles have extractors that sit flush in the bolt face, negating the need to time and cut extractor cuts in the barrels themselves (and timing can be done now CNC threading, so that's moot as well).
2. CNC machining has gotten to the accuracy level that mass produced, pre-fit barrels (and actions) can be done quickly and economically (much cheaper cost, as spread across volume).
3. Many gunsmiths have never made their living fitting barrels. More times than not, it was the little, mundane, menial tasks that paid for the lights to stay on. Fitting recoil pads, cleaning guns, replacing screws, swapping parts. There's a reason the hardcopy Brownells catalog has gunsmith prices (in code) on just about everything they sell (and why their catalog layout is copyrighted and patented). It allowed them to negotiate prices with customers (and see their costs in real time), as the customer decided what parts they wanted. But I digress...
4. The biggest reason pre-fits in the UK won't work (aside from the stupid proofing laws, which I fail to see how they could really effectively enforce) is because the gunsmiths will not change with the times. They want to fit barrels and do business as they have always done. But I will say this, and specifically to all the gunsmiths in the UK reading this, all it takes is one person to move to volume based CNC re-barreling...and you are all well and truly screwed. Make no mistake, there will always be the old school, hands on gunsmiths, but there will be a damned sight fewer of them, that's for sure. Lead times in the US used to run anywhere from 6 weeks to one year for fitting a barrel. Now, I can literally pick up the phone, specify the blank manufacturer I want, twist, contour and action pattern, and have a barrel in my hand in 7-10 days. Gunsmiths need to change the way they are doing business. Embrace technology for what it can offer, vice frustrate your customers (who could care less who, and more about what and when they can get a product). Times are changing.
Change with the times, or become part of the history...