Who lends the UK Government money?

[cakeorwine]

So we are borrowing a lot of money. Billions.

Who do we actually borrow it from?
What are the interest rates and the repayment terms?

We owe a lot of money. Just like other countries do.

But who is lending us - and are we 'good' for it?

We Brits lend at least some of it - Premium bonds, various other NS&I bonds.
Interest rates vary with the term. Premium Bond rates (calculated at chance of winning per annum) are very low, but not much different from most standard bank savings rates now. Savings bonds will be a bit higher if you fix (no access) for say 3 or 5 years.

They sell bonds, an IOU to repay plus interest

What happens if the amount of money needed just can't be borrowed?

Or is that an unlikely situation?

Plus a huge amount of the debt is owed to the bank of England itself.

Pension funds and investment firms, from the UK and globally. Ultimately much of it is ordinary people with pensions.

If not enough people want to lend, they raise the interest rate until they do.

And of course, they can just print more money like the feckless fucks they.