The problems are, as I see it :-
1) Lack of any sort of reliable radar service OCAS - It is hit and miss whether you get a Traffic Service from a civil unit, especially at weekends. Less than 50% chance I'd say. If everyone was using and encouraged to use a radar service around London, you could eliminate CAS busts.
2) Complicated airspace - the Airspace dimensions are not standard. Around London you have loads of different airspace altitude changes, different types of airspace and it is generally a mess. I remember seeing one post on here where someone posted something like "so if I pass south of Luton, so long as I'm above 2500 I'll be outide their class D" - yea you will, but in the Heathrow class A! why does LHR zone have to be so wide N to S? There is no need for it, you could have 1500' Class A base right next to the airport boundary and there is no way you'd have a problem with any CAT.
3) NOTAMS - difficult to visualise Lat / Long and lots of Numbers. I use SkybookGA which generates a route map with Notams drawn on the map. I also phone the 0500 number just before start up.
4) Navigation - Trying to DR navigate around the LTMA if you are unfamiliar is madness in my mind, with all these airspace changes etc....It can be done if you are very skilled, but in my experience with flying with new PPLs, is that they are not all that skilled!
5) Unclear charts. It is very difficult to see the LTMA boundaries on the half mil if you are not familiar with them. I had a look at some mil helo charts recently and they showed airspace so much clearer, with different colour shading in certain areas. Perhaps there should also be a "London terminal Area chart" published, like they do in the USA around large airports?
6) Mode C vale? Good idea, then my TPAS will provide reliable info
- in the USA you CAN enter a mode C vale without transponder as long as ATC agrees.