The North Sea CTA has a base of FL175.
http://www.nats-uk.ead-it.com/aip/cu...6_1_4_1_en.pdf
http://www.nats-uk.ead-it.com/aip/cu...2_2_1_3_en.pdf
http://www.nats-uk.ead-it.com/aip/cu...6_3_1_1_en.pdf
If you're routing direct VFR below FL75, there's no UK controlled airspace to affect to until you get within a few miles of Duxford.
Last edited by bookworm; 1st May 2010 at 15:28.