FlyingForFun
Time to hit the books I think
Transition
ALTITUDE in the open FIR in the UK is 3000'. Within various CTR's and TMA's however it can be different (East Mids 4000', London 6000', etc.)
Transition
LEVEL is a function of Transition Altitude and QNH, depending on whether it is above or below 1013 and whatever the Transition Altitude is. So, QNH 1001, TA 3000', TL=FL35. If the Transition Altitude were 4000' or 6000' the TL would be 45, or 65.
Now - back to the original query. There is no problem when flying VFR if you were to stay on QNH - you just report your level as an altitude. The only requirement really for flight on 1013 is for flight iaw IFR above the transition altitude, when you should report on Flight Levels.
Another thing to watch out for - base of Controlled Airspace. If it's designated as an Altitude make sure you're on QNH so that you don't bust it. If it's designated as a Flight Level and you feel you might get close then put the altimeter on 1013 to make sure - it stops you going where you shouldn't
CM