WH
A DA crossing service will be provided if it is safe to do so... DAs exist for more than just aircraft flying around, missile firings etc also require a DA.
It is very easy to give a DA crossing service in a piece of airspace several hundred square miles in size when it is being used by only a couple of Typhoons. Crossing a packed TMA is an entirely different proposition...
I work class A airspace in the LTMA. SVFR is not available in this airspace.
Class D airspace Zone crossings can be done under SVFR, subject to workload. I'm afraid that fee paying commercial traffic will always get priority, even though you are of equal flight priority. Any ATCO who refuses a zone crossing when they are able to give one, needs to be taken aside and re-briefed.
A commercial ANSP will not pay money to provide extra controllers just to give Zone crossings. In fact there is no need to, either the crossing is possible (which means that the workload allows it) or it isn't... having an extra controller will rarely make a difference if there is traffic to prevent the crossing.
The airspace in the LTMA is not ideal, but had been designed to try to give as much class G as possible. Any airspace changes have to be approved and it is a long drawn out process. Zone crossings are available, subject to workload. If workload is sufficiently high, then no amount of controllers sitting in would mean that the Zone crossing could happpen... because it would mean delaying the Fee paying aircraft.
Two final questions for you...
Do you think VFR/SVFR should be allowed in the Class A portions of the LTMA?
What are your thoughts on the VFR route proposed by SoaringHigh in his picture, i.e. the straight line from Shoreham to Cambridge... any potential problems with it do you think???