Thanks matspart3, very helpful. Come to think of it, he did give me the bit about the stepdown fix and MAPt. I was indeed squawking 7000 but it's nice to know that if it all goes pear-shaped, all I need is a radio.
If the radio transmitter failed, how would I go about requesting a speechless SRA? Is that what I'd get if I keyed . . . . (H) on the PTT, assuming that still worked?
Must try to find a quiet time for you and come back for a half-miler - I think 360BakTrak was a bit busy fitting me in with the VFR traffic as it was!
Tim