You have the requirements correct but the solo does not have to be "supervised" that would only be necessary if you didn't have a licence. You need 10 hours solo time on a SEP including the Navigation specified
10 hours solo flight time on SEP aeroplanes
which must include 5 hours solo cross country
flight time including one cross country flight of
at least 270km (150nm), during which full stop
landings at two different aerodromes different
from the aerodrome of departure shall be
made as per JAR-FCL 1.125.
You probably have enough to cover this requirement except maybe the 150nm X Ctry. If you do that don't forget to get the Certificate
SRG2105 signed.
Of the 20 hours you need with a JAA instructor, you say you have 8 already so you just need 12 more hours dual training.
The CAA will issue EASA licences from 1 July 2012, no JAA licences will be issued after 30 June 2012.
All looks fairly straightforward