The UK is one of the best places for bicycle touring. Watch out for the rain. I cycled the UK in the summer of 1984, and had only five days of light rain in seventy days. Be warned, however, that this was a freak summer, a drought summer, and that it is not to be expected to happen often like that.
The country lanes are absolutely the best. The English people are very friendly, and they give the best, most accurate directions when needed. Campgrounds and hostels are in abundance. Coastal areas and inland ranges compare for grandeur and scenic beauty with the pacific coastal route in the USA.