Wotan,
You are making an assumption that the CAA actually bother to police the EHS airspace regulations.
There is exemption available for Mode A/C only equipped aircraft in transponder carriage airspace until 2012, so outside of LTMA, state aircraft have some more time to sort their transponder replacement programme out.
The LTMA is the only EHS airspace (expect that to change later this year) and the original general exemption is due to run out, but as usual there will always be a special case for state aircraft. I understand that this issue is under review in UK to determine the impact.
RS