Casdon
My nearest town is the highest decile in Wales, it is is over 350 per 100,000. You can look up on the Public Health Wales website by medium super output area (c7000 population) to see what the rate is for the whole of Wales, I imagine probably for the rest of the UK as well. I wish you were right that at the levels in your area the virus is almost eradicated, but that’s not true - it only takes one party or similar work or social gathering for a flare up to happen very quickly -aka the Anglesey meat factory?
Yes, but the Anglesey meat factory was an isolated incident and seems to have been managed well. The big problem is in areas where hundreds of people are already infected and are mingling normally in shops, schools or in cramped housing.
As somebody upthread pointed out, the population of Greater Manchester is almost the same as the whole of Wales - and there are no mountains or bracing sea air.