Blues&twos,
You can do maybe ten circuits in an hour in a TMG, and you're getting used to glider handling at the same time.
High aerotows also give plenty of hands on time as well as lots of height to do the stall/spin awareness and recovery exercises, and of course you're learning how to aerotow.
Since you're not learning to winch launch, you don't have to do a dozen or so winch launch failure training flights.
A combination of motorglider and aerotow training is the quickest way to convert. You can book a motorglider session through the Lasham office, just as you would for power flying.