Off the top of my head legals and regulations wise:
- Your accountant can usually set up the Ltd company for you. (Or use a company formation agent if you prefer)
- VAT Registration if you expect turnover to exceed £70k (iirc) - easy to do, again your accountant will usually do this
- Bank account - most accountants seem to recommend Cater Allen (as they no doubt get a commission), good alternative is the co op.
- Insurance (Employer, employee and public liability insurance are legally required). You can get these packaged together, and doesn't cost a great deal.
None of which are actually needed to start trading online. I'd recommend just launching it, as a part time self-employed, taking payments personally and step up to a LTD co when you have proved it works. Apart from anything else you have a yearly overhead of roughly £2,000 a year to run a Ltd Co (including accountancy)
For your own sanity set up a separate account for business use - even if it's just a personal savings account with bank to take payments into and keep separate from personal things. You might prefer a "doing business as" account so you can use the trading name.
You will need to let the Revenue know (when you start taking income, or within 3 months) or they hit you with an auto £100 fine :
For payments also take a look at http://www.nochex.com/ over Paypal - UK based, their terms are better, and they have a business option to entirely free you from the risk of card fraud. (They're quite selective who's eligible for that option though). Good to get started with until you outgrow them.
If you're in the UK, selling to the UK also be aware of the Advertising Standards Regs as they now apply to websites, Distance Selling regs and Ecommerce requirements which say what you must have on the site. See here: