Def the ISA plan, think a couple can put just over £11k in per year, do the same again next week and thats £23k ish tax free and getting around 3% (which isnt a lot but all you cn get these days)
Be wary of some advice, after my mam died at New Year I found out she had been advised by her bank (northern rock) to invest £10k she had in an isa with L&G bond (not tax free, and not exactly low risk) not very happy with the whole thing and have spent some time trying to make appointments with those responsible.
good luck