There will come a point that my service will pass the vat threshold, and I'll have to charge vat. I'll immediately lose the instructors, and learners won't want to pay the extra 5 odd pound extra.
I know at the moment uber is fighting this case, I mean there not a taxi company and don't own or run any transportation company. They are literally a facilitator.
I wouldn't want to post my opinions on Uber on a public forum, blame rests with hmrc though for not ensuring they are treated in exactly the same manner as other UK based taxi provider "transport company" who provides a similar service. If hmrc can't operate a fair and transparent system for legitimate uk entities who pay rates/ corp tax and vat and who employee uk people so that they are not at a disadvantage it's more than a bit of a disgrace.
Anyway rant aside - all UK based businesses must deal with vat when they exceed the threshold so you are in the same boat as many and you just need to deal with that unless you can find the ability to create an offshore entity.
Getting back to your situation there is thankfully the option of setting up as an agent on behalf of the drivers (like Uber pretend to be) so that only your "fee paid/commission received" to the driver would be subject to vat and therefore you would follow the more normal route of simply paying vat on your "cut" which is nice and fair and will help pay for my nursing home unlike nasty Mr Uber.(oops off again) Note this is an area where you should get specific experienced advise to ensure the arrangements are set up in such a manner as to ensure there is no issues with the vat office - at a minimum buyers must be aware they are buying directly from the driver and and not you - you are as you say only the facilitator or "disclosed agent" (not so secret) as hmrc tend to call it officially, great care needs to be taken to ensure everything is done correctly though to keep hmrc happy.