FG,
I was in exactly the same position as you. I have kept my ATPL going after retirement but have Class 2 medicals. I had to renew it in 2008, so that year I had a Class 1 medical, paid the CAA a fortune and kept the ATPL going. (I must admit one reason for doing so is to keep my FAA 61.75 licence going and that is based on my ATPL.) I do a MEP LPC and SPA IR every year to keep the ratings in my ATPL current. I also keep the SEP validated.
What will happen after 2012 I have absolutely no idea!!!!!!
Fred