@stevie-s
I too am in almost exactly the same boat as you, expat from London living in Singapore like @sijfish, im at the very early stages of speaking to mortgage brokers about remortgaging my current property to release some equity to fund other BTL's in the UK.
What I have found so far from only 1 conversation with a mortgage broker is that lending for properties under £100k for expats can limit the number of lenders.
Have you or anyone else on this thread decided how you will manage the property from overseas e.g. a fully managed service provided by the letting agents or something else?
Interested to hear peoples learnings on any of this, this forum is such a great wealth of knowledge and information.