Agreed, OTA's would kill the idea of the business, it would have to be member based and built on long term agreements with providers.ebay and amazon fees are about 10%, holiday rental platforms charge between 10% to 20%.
Paypal charge between 2% to 3% on top.
Only dedicated web based platforms can deliver lower marketing cost for small operators.
Rambo, if you want to create a platform, keep in mind that if yours is successful, there will be a dozen copycats coming into the market within a year.
It's not just copycats who will threaten the business, a bike shop might see the volume and decide to do it alone gaining the few £ - all a matter of getting early on board and binding the shop owners to long term agreements.