The UK's Bank of England issues from Series A (1928) to the current Series G (Charles III variant) are surprisingly easily available, at least here in the UK.
The earlier treasury notes, the BoE “White” notes, and all the issuing commercial banks (or the forerunner provisional banks) can be much harder. The latter are the ones which really bulk out the catalogue. The BoE has always been quite focused & never bothered with commemorative issues.
The core BoE notes, I reckon you could buy one of each of them off the Internet today without any problems finding a seller. Finding them in higher grades, especially the higher valued £20s & £50s can be a bit trickier though not particularly difficult.
I've gotten an almost complete run from Series B (first issued 1957) and never paid much over the odds for them (though I admit, I accept lower, though still nice, circulated versions to keep costs down). I think my most expensive was a near UNC Series E £50 (mid 1990s) which I paid £67 for.
Series A is very available, just need to sit down & figure out the best value to note quality sellers.
So long as you don't go for signature variants, it's quite easy going. 34 (36 if you count the WWII emergency issues) notes I believe, so it's not a “cheat” nation with like 2 notes & you're done either. 😛
And you get a good flavour of how they've progressed over a (near) century, which can be interesting to see improving security features & the general “feel” of what the nation valued at the time.
Downside is cost as all the post-decimal (1971) issues are still exchangeable at face value at the bank. So, the five different £50s, 7 x £20s, 6 x £10s, and 6 x £5s, you will never get for less than face value. So that's at least £510, and that only gets you back as far as Series D.
Pro:
- Easy availability.
- Good range over long time period.
Con:
- Investment; though remember, you could exchange most of it back for face value if required on short notice.
- You might end up wanting to go for the commercial bank issues (currently still six extant issuers over Scotland & Northern Ireland), or the any of the innumerable extinct banks. And there's a lot of notes there, including many commemoratives. This is my current rabbit hole. 😬
