Before you spend money on an IFA OP, spend a few quid on reading up yourself.
Alvin Hall's "Your money or your life", is a nice lead-in to get you to start thinking about risk and timescales.
Tim Hayle's "Smarter Investing" is then very helpful when it comes to the nitty gritty of what to put where, and when, and WHY. If you have to read 1 book I'd make it that.
The citywire forums are good for getting a range of views and advice. I found out about some (low volatility) investment trusts there, which I hadn't come across before.
And MSE for basics - understanding the rules about the various tax wrappers etc. It is important to understand the tax implications as otherwise you pay more than you need to.
When I say you want to avoid making investments you don't understand - I don't mean "put it all in premium bonds", I mean, do the reading - get an idea of where the return/profit/growth comes from - understand how the charges work - look at the history of the investment - see what "old hands" like Warren Buffett have got to say about it.
I have done OK and did it myself - couldn't find any flat-fee IFA and didn't feel that confident that what they would cost otherwise was a sure enough bet. But that was my personal decision and YMMV.