Another vote for North Wales.Staying in Betws y Coed gives you easy access to Blaenau Ffestiniog mines (Slate) and the mines around Betws y Coed itself, (Lead etc).
Thak you for all your suggestions. North Wales looks interesting. Is possible to effectively travel there around using public transport or it would be better to go by car? Could you send me link to some timetables? We have the first oportunity to have our holidays in the middle of February but we`re wondering about rains which could increase the water levels underground. How is the weather at that time?
.....the water level remains (almost) the same through the year.
It never rains in North Wales.
I would recommend hiring a car if possible. I use buses and find it a real hassle carrying lots of kit on them, especially on the way home after a trip when everything is muddy or dripping wet. Public transport in rural Britain is far from ideal with regard to routes and frequency, especially on Sundays.