Not going to advise on whether to invest or not, but in considering options, don't forget the booming small-medium sized towns.
I can name one town where between the 7 estate agents you would be lucky to come out with a handful of rentable properties and the demand is huge, driven from retail and commercial growth locally. You don't need me to tell you what that is doing to rents.
In looking at interest-only versus full repayment method, the rents are coming in at midway between the two. So small and manageable shortfall if going with repayment option, and small yet useful surplus if going interest only.
Don't limit your choice to city and section properties.