Don't know what UK your talking about, its not the one I live in. In the city centres its busy with limited area's and park space but else where is quite rural.
The largest land owner is the forestry commission, own and maintained by the government for the public use and which has been expanding the UK's forests and woodlands for decades.
93% of the uk is classified and not urban and of that 7% that is only 2% is classified and not natural.
Most cities and towns have over 50% green space, parks, allotments, sports pitches etc
http://www.bbc.co.uk/news/uk-18623096 have read its enlightening.