Cash ISA with the best rate you can find. Try Nationwide, they are still a true building society.
Investing is generally longer time horizons than 5 years. You could, however, put some into ETFs. Hard to do with a smaller amount as you only want to buy one or two.
VEUR.L is one I'd look at, as it is all of Europe (inc UK). With someone like iWeb Sharedealing.
But yeah, if you can't afford lose a chunk of it in the short to medium term, cash ISA.