You only get one crack at sorting your retirement and you really cannot afford to screw it up.

I really dont think property investing is appropriate for retirement funds unless you are an experienced investor and have a lot of market knowledge.
The problem with any property investment is liquidity.
generally your risk profile should narrow as you age so that by the time you retire your returns are derived almost exclusively from fixed income.

I have had lots and lots of expatriate clients asking me for help recently. The reason for this is that they have all their money tied up in their homes and have ran out of cash for whatever reason - business failure - downturn in economy - poor health.

But, unless thy can actually prove sufficient income thy cannot even release equity - unless they are 60+ and wish to utilise lifetime mortgages. This is unbelievably common and its a killer when there is nothing you can do to help someone other than suggest they put their home up for sale or for rent.

So, depending on where you wish to retire to, I would stick to very low risk liquid investments.
You can easily achieve 6.5% pa tax free if you are outside the UK.
If you can tie your money up for 12 months - 8% is available for expats. If you are really intent on property investment you need to be extremely cautious and only invest what you can afford to tie up.