I can be trading within 3 days.
Not that impressive considering you bank with them. Most of the big execution only brokers can have you trading within an hour provided all your details check out
I’d strongly suggest reading up on capital gains tax (CGT) and tax free allowances here: http://www.hmrc.gov.uk/cgt/shares/basics.htm
ISAs are great for sheltering your profits from CGT but you’re limited to how much you can subscribe each year and many providers levy charges for admin (usually waived if you’re account is valued over a certain amount)
My advice would be to go with a broker that offers competitive rates on commission charges, low admin fees, has a reliable web and mobile platforms and provides access to good market data and research.
(HL are regarded as the best for most of the above and their customer service is supposed to be top notch.)