With my old rare and beautiful Jaguar I used to do a couple of things, the first is try and park facing a wall. and second I used to use a steering wheel lock that covered the entire steering wheel, I cannot remember the lock name but it was bright yellow with black writing on it. It had a built in hardened lock, and a really strange style of key. It was heavy and a PITA to store, but unless you had the key it was not coming off, with the steering turned on full lock even with a set of 'specs' it could not be towed away, certainly helped me sleep at night when I could not park it in the garage when not at home, in fact I used to use the steering wheel cover locked even when in the garage at home, I still have the Chubb insurance approved hasp/staple and lock that used to be on the garage doors, the insurance company insisted on me having that, in fact I still have the lock in my storeroom, and it really is a beast! Either way the wheel cover was a lot easier to remove and slip in a padded bag than faffing around with a wheel clamp.
My 3 litre Capri GXL had a removable steering wheel, but doubt there is a quick release steering wheel available for the 80, the 'squib' would be a problem for air bag models.
Regards
Dave