If you don't need it for 5 years you could tie it up in a term account that pays a higher rate - but you won't be able to get at it at all for the five years.
Make sure you're not carrying debts costing you interest (paying off debts is always a good idea) or pay off some of your mortgage or off-set your mortgage - if you have one.
Make sure you and your partner (if you have one) have used your ISA allowances for this year.
Over five years, you can afford a bit more risk; if you have maxed your ISA contributions for this year, hold off until April 6 and then put �7,200 in a maxi stocks and share ISA (protects gains from tax; choose a fund that matches your appetite for risk) for 2008-09; your partner (if you have one) could do the same; that would leave say �16k to invest....
If you have children and want to save for their futures, you could set up stakeholder pensions for them - the money would be tied up until they are at least 55 so they couldn't squander it in their teens!
Just some ideas. NB - I am NOT a qualified financial adviser; THE BEST THING TO DO is talk to an INDEPENDENT financial adviser who operates on a fee basis (like consulting a solicitor) and NOT on a commission basis. Ask family/friends/workmates for personal recommendations.
Hope this helps.