When looking at recordings of popular composers and popular performers on the major labels, chances are the same recordings have been released and re-released many times as the record company tries to continue cashing in on works already in their archives. There may also be used 'record club' versions of the albums which are less valuable, but which have the same sound quality as the original release. Thus, keep an eye out for the same recordings on other albums.
In the last decade or so, the major labels have been producing 'bargain' box sets of these popular works. In the case of those Karajan Sibelius recordings, this certainly seems to be the case. Klassik has not looked carefully (and, frankly, Klassik is not much into the music of Sibelius and is even less into the performances of Karajan xD ), but at the very least, DG released in 2021 a complete set of Karajan recordings of Sibelius music on the DG label. It consists of 5 CDs and a Blu-Ray Pure Audio Disc. The price direct from DG is 26 Euro. That might be a bit much if you just want one symphony, but the price isn't bad if you want all of the Sibelius that Karajan recorded.
https://store.deutschegrammophon.com/p51-i0028948606511/herbert-von-karajan-die-berliner-philharmoniker/karajan-sibelius-complete-recordings-on-deutsche-grammophon-5cd-box-/index.html
Klassik knows not about UK classical music vendors other than Presto Classical. To Klassik in the US, Presto's prices seem reasonable. Here recently in the US, there has been consolidation with popular classical music online stores. Klassik liked the HBDirect store out of Vermont, but it seems they were bought by ArkivMusic operation which itself is owned by Naxos Klassik does believe. The end result is higher prices, higher prices for shipping, and fewer promotions. :S At least something still exists though, right? :/
Klassik has purchased some of the aforementioned bargain box sets. That said, Klassik generally listens to more obscure music than popular works and so one cannot be picky about those. Often, those works are only recorded once or twice. Take what's available and like it or don't. Oh well, there are still good discoveries to be had and Klassik likes browsing the local new/used media stores to see what interesting things they have. Here recently, they have a lot of closeout Hyperion and Brilliant Classics CDs and there are some good bargains to be had on unopened classical CDs. Klassik knows not if such stores exist in the UK, but if so, they might be worth a look. The new/used media store also has many used CDs.
Back to the topic of box sets and re-releases, there might be a practical benefit to buying a newer re-released/box set version of a work rather than an original CD from the 1980s or early 1990s. Many of those older classical CDs had pre-emphasis and that can create issues with outboard DACs and when ripping the CDs. The end result is often overly-bright sounding music. Modern re-releases will probably eliminate the pre-emphasis so that the CDs can be played back and ripped with more expected results.
