iWeb stock and shares isa

Should I choose one fund or a basket of funds.

If you have strong ideas about what you would like to put in the basket and want to be hands-on, then using a basket (portfolio) approach is the obvious way to go.

Whereas if you don't particularly care about the minutiae of asset allocation, and struggle to make a decision between two different styles because they both have their pros and cons, you are probably well suited to using a mixed asset fund where someone else takes responsibility for portfolio construction and maintenance to deliver the target objective. Ultimately it's your responsibility rather than ours, so if you want to 'hedge your bets' by buying a bit of two funds instead of just the one, no harm done.

I will probably keep My Legal and General Multi Index 6 where it is as it does not seem worth moving over to IWeb for a 20k investment as the savings on charges would not be that significant

If you're putting £hundreds of thousands in one platform, it can be good to have some investments somewhere else, just to ensure you can get at some of your investments if there is a problem with that 'main' provider.

That said, you have loads of cash so unlikely to be bothered by some administrative issue on a fund platform on which you are tucking a fund holding away for a decade. IWeb accounts are essentially free to hold a fund other than the account-opening fees and initial transaction cost, whereas if you continue to go direct to L&G you will be paying a premium level of charges built into the management fee, so that they can afford to run their direct-to-customer front-end.

As such, if the exact same L&G fund is offered by IWeb as a cheaper share class, (i.e. with a lower ongoing charges figure than going direct as you are now), you might as well move that £20k to IWeb. Might save you £50 a year on £20k for little effort.