The appraiser also seemed to exclusively use Zillow to find properties and 2 of the subject properties had their leases end this year. 

I’m in Charlotte, NC but I manage over 50 MTRs almost exclusively.

Some are doing it to the exclusion of representing the consumer home buyer.  

ROE is so low (.6%) that at this point in our RE journey, we believe our $$ can do more for us elsewhere and we still sit within Sec121 exclusion to avoid some CG tax. 

Overwhelmingly Positive Testimonials and Reviews from StudentsThe "reviews" for a guru come exclusively or overwhelmingly from individuals who create accounts on BiggerPockets with seemingly no other purpose than to dispense undying love and/or personal loyalty to the guru, with lengthy commentary about the complete life turnaround that spending $5K - $100K had in a very brief period of time, rather than a rational assessment of the pros and cons of the program and their outcomes achieved so far.  

Even with a exclusion of gain under Section 121 (MFJ: $500k), they are looking at over $100k in taxes from a sale.

I remodeled many old Craftsman houses in an exclusive little beach town in SoCal.....Every single one went from closed-off to open concept and ended up looking better.

I like having one account exclusively for rent payments and another for security deposits.

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?

Get to go slow and learn over time, build capital, and qualify for the primary res cap gain exclusion.