Thanks for all your responses.
I don’t have a problem getting the front wheel up – that bit I find easy.
It’s finding (and holding) the balance point that I find tricky.
What I found helped though, was getting my arse down low and well over the back wheel. Makes sense to keep you centre of gravity as low as possible.
Another thing I found helped, was getting the front wheel up smoothly, rather than doing a massive pump which gets you off to a shaky start.
Perhaps I should try practicing on flats – I think there’s probably a bit of mental block at the back of my mind, which keeps me on the low side of the balance point when I’m clipped in.