This.
@Aoap78 are you planning to invest on a regular basis or is this a one time windfall that you're looking to grow?
Will you need access to the money at short notice? Are you likely to panic if your investments go down during a market crash or would you be willing to ride things out?
If you don't plan to make regular investments, avoiding ongoing charges would be desirable.
Most ISA providers charge either a management charge or a funds charge or both.
Interactive Investor charges a set monthly fee no matter how much you have invested - but you don't have a huge investment, so it might end up being quite high as a percentage of your holdings. They have free regular investments, which is good if you're investing each month.
AJ Bell charges a percentage of your holdings, but it's capped. They also charge a percentage of any funds holdings, but not for stocks and shares. They charge £1.50 for any regular investments.
iWeb (now Scottish Widows) are free to open an account. They have zero ongoing charges for stocks and shares. They charge £5 a trade, but don't offer a regular investment option. They charge a percentage for holding funds.
If you're planning to just buy a global tracker ETF (I invest in a legal & general ETF LGGG), iWeb might be best. You'd pay £5 to buy £5000 (which is 0.1%) and then you'd have no further ongoing platform charges. It could sit there for years and you wouldn't have fees eating away at your capital.
If you're planning to make monthly contributions, then Interactive Investor or AJ Bell might work out cheaper over the year. You'd have to work out the likely annual fees and make a decision.