The spindle belt tension is adjustable by loosing the bearings for the pulley, they should be mounted on slots, just pull the shaft over and tighten then adjust the bottom pulley tension to compensate the change in the lower belt by tightening  or loosing the justifiable rod used for speed change. Hope this makes sense, if you read this whilst looking at the belts it should help.

Hi, I think it’s only the Vari-Speed and the MK. 1 that have the adjustable bearings, mine is a MK. 2, and the intermediate shaft has fixed bearings.

If you take the belt off the pulley on the intermediate shaft, and let it hang loose on the R/H side, then put the belt onto the spindle pulley, you may be able to use a bicycle tyre lever, or something similar, to lever it over the intermediate shaft pulley, while turning the spindle, via the chuck or the belt on the stepped pullies. If it won’t go on without undue force, your belt is probably too short. Yes the quality of the link belt will make all the difference, Brammer link belting is one of the best, but can be pricy.

Regards Nick.