If you want hilly events then look for Grimpeur Audax rides.
They'll probably be a lot easier to get to than the Alps (as long as you live near some real hills).
Plus you can start off with a shorter 100km ride (still with 2000m+ of climbing usually).
http://www.audax.uk.net/ then click on Calendar, then select "AAA only" as the ride type and hit "Show".
If you need/want time to train, and want a real challenge, then consider the Midlander Super Grimpeur from Sutton Coldfield. 26th June 2010. 300km and 5390m of climbing. Stunning ride, across the length of the Peak District, twice, and I certainly felt the hills when I did it this year.
