If you’re looking at an 18 year return period, you’re probably as well investing in a shares ISA, as the tax free amount is a lot higher (a bit less than £6k and you can dump the rest into a cash ISA I think).
Alternatively, now is a good time to be investing in shares – a split between financial institutions, mining and pharmaceutical companies will more than likely yield good returns over that timescale – people will always need medication, money and raw materials to make stuff. Whilst there’s a lot of noise about stock market losses at the moment, over a 10-20 year period, the stock market will outperform inflation.
Well worth contacting an IFA – they’ll take a commission, but you’ll more than get that back. I’m happy to recommend a good guy who has saved me thousands from the robbing bastards at Nationwide…