Hi FFF,
No fixed wing SVFR routes are published for the London CTR. There are sound reasons for this which I won't mention here. There are several routes which are commonly used by SVFR aircraft, and these have developed over the years by custom and practice. The BUR - ASC route is one of these. It can be used when Heathrow are landing on 09L/R as it passes under the final approach track at 7nm. Aircraft descending on the ILS will be at 2000ft, SVFR traffic not above 1000ft - standard separation. On Westerlies at Heathrow, departing traffic has to cross the noise monitoring point at 1000ft or above and maintain a minimum 4% climb profile which equates to 243ft per nm. By 7 nm West therefore, departures should be at 2000ft or above and therefore separated from SVFR traffic at 1000ft. The SIDs cross BUR (or its vicinity) at 3000ft or above, thereby allowing climb to 2000ft (if appropriate), for Northbound SVFR traffic.
As I mentioned above OCK - BUR comes too close to Heathrow for comfort, and also too close to the Fairoaks LFA. As I said, take a look at a map. The other issue is that traffic on SVFR clearances is supposed to be navigating by visual reference to the surface - not beacon bashing.
OK, your flight from EGLM - EGKR. Call us in the White Waltham circuit for a clearance, not en route to BUR or ASC. There may well be other traffic already established on the routes and we have to provide standard separation between you and it, which can be difficult to achieve in confined airspace. Not much point in calling before you depart - the traffic situation can change rapidly. Stay in the circuit until you have received a clearance which will include a squawk, a routeing, a "not above altitude", and the London QNH.
The return trip. No point in routeing back to BUR - that is out of your way. OCK - WOD is a common initial clearance with a direct track to EGLM when South abeam ASC. (Or even OCK-ASC- EGLM). Always ensure you avoid the EGTF LFA or call them to warn them of your presence, and always be prepared to route around the Zone if a SVFR clearance cannot be given for any reason. We will transfer you to EGLM when you are clear of conflicting traffic - you will usually be asked to retain the squawk until the circuit.
Lastly, I am surprised about the lack of knowledge and reticence about SVFR clearances, especially at airfields within the LCTR. There must be instructors available who will explain the procedures and the requirements for SVFR flight to PPLs?