OP, if you are abroad then you will have to deal with the wonders of international taxation and international tax treaties. You may have to hire an accountant who is familiar with the tax rules of both the UK and wherever you live; that will add a lot of cost and headache.
Also, a common mistake is to calculate yields and returns excluding all the costs.
Say you buy a property with a £50k deposit, but spend an extra £15k between stamp duty, legal fees, furniture etc. Your investment is £65k, not £50k. Let's say that, after tax costs mortgage etc you get £2000 net per year (I'm just making this up). The net yield is not 4% (=2/50) but 3.08% (=2/65).
Also, if/when you sell, the property must have appreciated enough to cover your stamp duty, upfront costs, agency fee and capital gains tax (if applicable) just for you to receive back what you put in.
Say you buy for £200k with a £150k interest-only mortgage.
You sell for £230k.
Your net proceeds will be something like:
230
- 6 (between legal fees and agency fees)
- 20% * (30 - 15 - 6 ) [you can deduct stamp duty, legal fees and other costs that increased the property's value when calculating capital gains)
= 72.2
So you invested 65 and got back 72.2 (plus all the rental income in the meanwhile), which is fine but lower than it looks if you ignore the costs.