Hi Dimensional,
I will be working Thames Radar on Saturday morming. The only complication is that there is a calibration of the 28 ILS on Saturday. I suggest you plan your flight for early afternoon when City Airport is closed for the best chance of a zone clearance.
Runway 10 in use is marginally easier for transits. Coming from the South you might be held outside the zone North of Crystal Palace or alternatively at the Southern tip of the Isle of Dogs. Coming from the North you might be held at the "Southernmost Lake in the Lea Valley" so get hold of a map and be prepared for these eventualities. You do not have to file a flight plan - we just need basic details of your flight (which I am sure you have covered during your RTF training). It helps if you carry a transponder. If you are told to standby and the frequency sounds quiet, wait until we get back to you and do not enter the zone without a clearance. There is an awful lot of telephone co-ordination on Thames which will be transparent to pilots. I try to give a "not above" VFR clearance which is usually 2000 ft, but will vary between 1500 ft and 2400 ft depending on traffic. Be sure to comply with the controller's instructions which may be to pass East/West/Overhead City Airport, and watch out for the plethora of other traffic - pleasure flying helicopters, police helicopters, Helimed, Capital Radio, Classic Wings Rapide, the pesky "Dome Watchers" etc. etc.
I hope this answers your questions - if not e-mail me.