I had my first S&S ISA with Hargreaves Lansdown and was with them for several years. They have an excellent platform and customer service, are beginner-friendly, and in common with other established platforms have a much wider range of funds and stocks than Freetrade currently has.
Their platform fee is % based (0.45%). Depending on trade types and patterns this can work out cheaper than fixed-fee platforms when starting out (even compared to Freetrade ISA’s very low fixed fee) but at a certain point will get more expensive.
So one option to consider is to begin with a % fee platform and then transfer to Freetrade ISA just before your fees start to exceed Freetrade’s fixed fees (assuming Freetrade has started to support ISA transfers by then). Something to be aware of with this approach is transfer out fees. Lots of platforms (including Hargreaves Lansdown) sting you with these. If you do plan to start an ISA at a % fee based platform with the intention of transferring to Freetrade at a later date make sure you look for a platform that doesn’t charge transfer out fees. As has already been mentioned, Vanguard Investor is an excellent option to consider if you are happy with being restricted to Vanguard funds. They charge an extremely low % platform fee (0.15%) and don’t charge for transferring out.
I suppose another option is to use the the Freetrade GIA until you have a gain just below the CGT allowance or a holding just below the annual ISA allowance and then sell it and re-buy it within Freetrade ISA. An issue with this is you would use your entire ISA annual allowance for that year in one go.
I recently transferred my ISA from Hargreaves Lansdown to the fixed-fee Interactive Investor. At £90/year they are more expensive than Freetrade, but Freetrade isn’t an option for me right now because it does not accept ISA transfers yet. On the plus side, the platform fee at Interactive Investor also serves as trading credits (so for my trading pattern I won’t be paying any additional trading fees) and they don’t charge transfer out fees.
I chose Interactive Investor over Vangaurd because the fee for me is not that much higher than at Vangaurd, I want to hold more than just Vanguard Funds, and they currently have a cashback promotion which covered most of my HL transfer out fees. Haven’t been using long enough yet to comment on the quality of their service.