Hi Geoff,
I would be careful with the Sports hall floor job....
They are generally covered in a specialist sealer made by a company called 'Granwax'.
I have had to strip and reseal them for a couple of Leisure companies and it's a killer.
Special Stripper, special sanding discs, special applicators and 'special' sealer which is very expensive
The lines are mostly painted on with 'special' lining paint.
I recently turned down a job to reline and refurb a Gym.
The money can be quite good but believe me , you'll know you've earned it.
Les