I have a cross flow, and have gone through bad starting and battery and starter motor change. I live in Wilts, so am happy to offer any adivce/help. Getting the battery out, can take a little time, mine can be removed from below the car, if you have a cross member that runs under the battery, then you have to take off the carbs and move the steering linkage. This depends on the year of the car.
Charging the batter in situ, is easy, and takes differing time, I normally charge overnight on a trickle charge.
Rgds, Robert