In reply to yorkshire_lad2:
Thanks for the recs for q-park. I ended up in Citpark on Whitehall Rd (as better access when approaching from Ilkley and Swinegate would have been a bit further, but probably good if accessing from the south etc).
https://citipark.co.uk/car-parks/leeds/7-whitehall-road
Easy to find, open and airy, easy online pre-booking, about 5 mins on foot to the back of the station. Apparently it's possible to walk along the canal path to the station but I went along Whitehall Rd as I didn't fancy the canal route late at night.
No connection with Citipark other than as a customer.