Why not invest in an Investment trust...there are hundreds to choose from.
You could select one or more that you are happy with...as with any investment there is a level of risk involved. But as you are investing over the longer term it would be unwise to not expose the money to the growth available in the stockmarket.
Also you are saving on a regular monthly basis and therefore lessen the risk associated with lump sum investment.
You will gain the benfit of pound cost averaging...Have a look here as it is better explained than I ever could
http://tinyurl.com/yfwuwye
Whatever you decide do not put it in a ...Safe ... Bank savings account...inflation will just eat away at it.
Get some proffesional advice from an... Independant Financial Advisor ...
You dont have to deal with them...just take the advice...and do it yourself.