Sage - help with changing end of year date please

We are trying to change the year end on Sage 50 2010 (V 16).  The client set it up originally as 1/1/10-31/12/10, however the year end (first) is actually 31/5/11.  Getting the figures for the accounts has been OK using 2 different periods but we are now trying to change the year end on sage to May and run a year end at this date (after running the Dec 10 year end).  All we seem to be able to do is keep to the Jan-Dec period.  Sage say they will change it for (of course) their fee which is never cheap but I can't believe this facility doesn't exist as it is a normal occurrence for companies surely.  Sage is not my area of expertise so any help gratefully received.

Thanks.