Well, one GA pilot now understands a lot more about separation. Thanks, everybody.
My conclusions, which will become part of my modus operandi, are as follows:
a) It's OK to route close to the boundary of CAS, but separation from traffic inside may be less than desirable. So avoid being too close vertically and laterally unless for a specific reason, such as avoiding other hazards or because of high ground below.
b) Therefore in VMC keep the usual good look out -- But looking inside CAS as well as other directions.
c) In VMC, contact the (Class D) controller for FIS; this will allow mode C verification as a minimum to help with TCAS alerts, and will give the controller the knowledge that almost professional and ATCO Two would like.
c) In IMC definitely make contact and ask for RIS or RAS. If I'm in IMC just outside CAS, the traffic inside will probably also be in IMC, and close TCAS alerts in IMC are not good for anybody. If no service is available, don't get too close to the boundary.
d) It does seem that I'm making life harder for you by becoming known traffic, rather than remaining unknown (which you can 'deem' to be separated), but in this case, harder does mean safer for all. Although, I suspect Slaphead is talking common sense when he says he deems traffic outside CAS which has contacted him to be separated. [Slaphead - I assume you are talking about VMC?]
e) I will continue to request transit when it makes sense to do so. Both Luton and Essex seem to be much more willing to offer clearances than a year or so ago, something which I do appreciate. Some days and in some places I would much prefer to be in CAS than outside. LAM-BKY is much safer than LAM-BPK-BKY, even in good VFR.
Two questions still in my mind:
Do the London TMA controllers working the area close to EGLL want to hear from GA traffic just under the TMA base? I assume not, on workload grounds. (HD or 120.4 any comments?)
Should a better understanding of ATC procedures be a bigger part of GA pilots' training or information resource. For example, should this separation issue be covered in an AIC?
Finally, ChrisN, the On Track team will be reporting fairly soon, I believe, so we'll know more about the reasons for airspace busts. However, this is really off this thread and is a very different issue.