SBing through a UK Limited Company rather misses the point. Regardless of any issue of interpretation and implementation of HMRC rulings, which are various and seem to depend on your local geography, taxes on income derived solely from SB profits being liable to personal taxation or not are lost as you move into a corporate structure.
If you make profits through SBing or any other endeavour through a limited company, when you take money out of the company through salary or directors dividends, you will be liable for personal income tax and NI contributions. And corporation tax potentially on any balance. Plus the costs of incorporating, running and auditing the company.
Absolutely no benefit.
If you’re determined to make a living from SBing, and the very best of luck if you are, or think you are, your best route in my view is to go along with the assumption and received opinion that all profits from SBing are tax free. If you are pulled up my the forces of darkness, fight with all your energy and make nuisance – do not go down quietly. These goons have targets just like all pencil-pushers and if you’re causing them personally too much time, energy, frustration and grief, they are more likely to leave you alone and go after other, easier targets. Worse case is that they find against you and take what you would have paid them in the first place had you voluntarily offered up your hard earned gains to the offices of HM official extortionists. Plus maybe a fine if you take it too far. The trick, as always, is to gauge where you are in the process and when to cut your losses. And of course, to weigh up the probability of you coming to their attention on the first place.