If you are 550 ex-aircrew then the following may be of interest to you.

A friend of 550 Squadron Association is a 'Monday' Guide at the BBMF at RAF Coningsby, who will 
give special attention to members of 550 Squadron Association when they visit.

So ... if you visit on a Monday it may well be possible to arrange an opportunity to go aboard 
PA474 the BBMF Lancaster (subject to the condition it is in, on the day).

Key points:
1.  Make yourself known at the Visitor center reception and that you are 550 ex-aircrew.
2.  Ask for Arthur Punchard.  
There is no guarantee of access, but with luck, a fair wind and the hope that the BBMF Lancaster is not 
undergoing refit/maintenance, or is otherwise out-of-bounds that day, then maybe you could get up close to PA474.

		Website: http://www.raf.mod.uk/bbmf/visitorscentre/