Best performing stocks and shares ISA?

Hi oilrag
An impossible question to answer as the performance of a S&S ISA will depend on what you invest in inside the ISA, rather than the company you hold the ISA with.
As you can invest in 10's of thousands of Unit trusts, Shares, Investment Trusts, Gilts, RTF's, warrants, etc, it is more a question of which one do you pick. And it will only be at the end of the period you invest for that you will know whether you picked the best, the worst, or one in the middle.
You can of course go to an investment company and pick one of their tailor-made investment packages that best suit your level of risk.
I include below a link to a company that i currently use to manage some of my investments. I cannot recommended them highly enough for the service they offer, but by way of balance there are a lot of similar co's who will also offer a similar service.
http://www.hl.co.uk/investment-services/isa/why-invest-in-a-stocks-and-shares-isa
Even if you only read what they have to say on the subject, and then invest elsewhere, they will give you a good understanding of running a S&S ISA.

This is a very common misconception about both Stocks & Shares ISAs and pensions. They are neither good nor bad, just tax wrappers. What you invest under this wrapper will determine how they will perform.

Hi,

Bonz is right - hargreaves lansdown is excellent for open ended funds.

If you wanted to go through a self selection route and pick out shares, closed ended funds and ETFs/ETCs then I'd suggest iweb as its dealing costs are lower and there's no annual ISA charge.