I do both of these all the time.

Which one is cheaper tends to be a crapshoot, though if forced to guess I'd say that Transferwise is usually cheaper. Visa/MC exchange rates change once a day, whereas Transferwise updates their rate much more often. Transferwise gets a little less than 1% in fees for USD -> GBP, but Visa/MC's rate is generally off by around 1%. Either way, we're talking a tiny difference--maybe enough to buy a couple cups of coffee--unless there's a major exchange rate fluctuation during the day or you're moving amounts of money that are too high to get out of an ATM and more than I'd want to schlep around in GBP 20 notes :D

OP, it sounds like you trust the B&B owner, so if you don't want to deal with a stack of 20s I'm sure she'd be happy for you to send payment with a bank transfer, which you can do easily with Transferwise.

Having thought about it some more, the trouble with a bank transfer is the mess we might find ourselves in if we had to cancel the trip after we'd initiated the transfer and I had to rely on her to transfer the money back to me. The last time we stayed at one of her properties, she was happy to come back a day or two after we'd arrived to collect payment, so maybe she'd be OK with a bank transfer after we arrived?

I'm beginning to think a stack of 20s is the simplest solution.

Just make the transfer a few days before your trip when you're sure you're going?

I think you will find it her preferred solution too ;)

We're bringing a 10-month-old with us, we won't be "sure we're going" until we board the plane.

Yep. Simplest all round.

The bank may take the old £1 coins off you if you ask nicely, although they often restrict it to customers. Try a Post Office too. Failing that, as mentioned above, your landlady might be willing to do it. If more than £20, bag them up in lots of 20 (bags available from a branch).

Thanks, I'll start with the Post Office.

Yes. The landlady will not regard it as 'low class' - rather if you gave her a load of £50 notes she'd probably regard that as a pain in the a**e!

I must say I'm surprised - my bank wouldn't hesitate to except $50 or $100 bills to deposit in my accounts there, provided they weren't counterfeit. Granted, not every business would be happy to accept them, even genuine ones, but banks certainly would.

There'd be no problem depositing them at a bank. It's paying shops and businesses, trades people, cleaners etc with £50 notes that can be more problematic.

Your landlady is unlikely to be depositing your cash into the bank. She will prefer the £20's as she will be using them for normal spending and they are the desired note. I have not had a £50 note in my pocket so far this decade - and can't recall when I last spent one, whereas in the same period I have had and spent loads of US $100's and $50's - it is the way we do things here! UK ATM's don't issue £50's, only £20's and £10's.

The whole premise of this thread is a bit confusing.

If you needed to pay $500 in cash in the USA, would there be a problem with 25 $20 bills? What about $1000 in $20s? Is that considered "low-class"???

Although I find counting US bills to be more difficult, they don't slide easily off each other like UK paper notes.

Though of course if we only consider Bank of England notes, the £5 and £10 are polymer (plastic) already and the £20 and £50 are heading that way (the new polymer £20 is coming in 2020, the £50 later). And several of the Scottish notes are polymer already.

I have odd notions of what is and isn't low class.

And the Northern Irish polymers have just come out!

Going OT, I find that Australian series 1, Australian series 2, Canadian, UK and NZ polymer notes all feel very different from each other, and Canadian notes have a distinctive smell too.