Simple blueprint for long term tax planning

[TheFaQQer]

With this pension drawdown approach, does that consist of taking a tax-free lump sum at regular intervals until the pot is empty?

It can do - you can regularly withdraw a lump sum tax free until the pot is empty, or draw some out and invest the rest, or draw some out and buy an annuity.

If so, how does the HMRC get its tax?

If you just withdraw each year, then there is no tax to pay (up to the limit). The danger of this is that you exhaust the pot before you die.

Am I right that interest paid on my business bank accounts is also taxed? Or rather, untaxed at source but treated as income for the company?

It's income which the company then pays corporation tax on.