Hi Guys 'n' Gals
Found a good pdf document showing all the low flying and transistion areas in the UK (any that not show are new or are temporary etc are show in NOTAMS). Of particular interest are the Military low fly training areas. This will help with Nav exercises and avoiding these will probably help prevent an nasty unexpected shock as you poodle along your planned track
http://www.ais.org.uk/aes/pubs/aip/pdf/enr/6_5_2_1.PDF You many have to register with NATS but it is free and has loads of good info