And they have a huge amount of beaches much nicer than Tulum's or Colombia's, which are much more easily accessible from pretty much anywhere in the world where most tourism originates.Yet, they won't do it.

This is one of the reasons I would be very hesitant to allow an arbitrager access to my property.

Is this market accessible for the average investor in the UK, or is it exclusively banks and hedge funds who buy/sell these sorts of instruments?

There are different philosophies to real estate investing and it depends on your finances, if you have less capital, you're going to have to be more creative on deals and need cash flow, if you have access to some capital, you can tolerate cash flow losses.

@Kerry Baird so to be clear  this BLOC is never reported on your DTI if you have accessed it?

If you really want to fine-tune it, you need an agent with MLS access to run the on-market rentals which are a fair representation of what you can expect.

Or you have to be the lowest barrier of entry-- meaning really convenient price and easily accessible location.

There is a way to do shared access if you are not concerned about this.There may be other options out there, but this one does not require a plumber and is easy to install.

I only access their websites via my phone. 

Offer my services to existing investors so I can learn first and have access to their networks.2.