We were looking at interest only mortgages for a relative recently, although the initial 2 yrs were attractive the rate after that was not so attractive, your age and income was probably not a fit for that type of mortgage.
In our case the prospect of £670 interest payments compared with £800\month rent and holding onto the £50K deposit seemed a better option, here is a typical calculation we had.
Representative example
Borrowing £150,000 over 20 years, representative APRC 5.1%:
Initial term
24 payments of £373.75 at 2.99% (discounted)
End rate
216 payments of £667.50 at 5.34% (variable)
Total interest
£153,150.00
Total upfront fees
£1,029.00
Total amount payable
£304,179.00