GreenMan Gaming have Destiny 2 Expansion Packs in their halloween sale

They have several of the most recent dlc packs available some for fairly high discount

These are US prices not sure what the UK prices are like hopefully fairly similar

The destiny 2 legacy collection is 57% off at $25.50

That includes the older content, Forsaken Pack and Shadowkeep which have some content but not a lot a few older dungeons and raids there. It also includes Beyond Light which is the previous expansion pack which includes the Europa Destination as well as the new Statis subclass as well as some story missions for the Beyond light campaign.

That feels like the best value for money option it gives you all the old content as well as the statis subclass. You can get some of the packs like beyond light separate but they are not much cheaper so feels like the best bang for buck

https://www.greenmangaming.com/games/destiny-2-legacy-collection-pc/

If you just wanted the beyond light and wanted to save a few quid they do it for $15.29

https://www.greenmangaming.com/games/destiny-2-beyond-light-pc/

They also have the most recent DLC Witchqueen for relatively cheap normal version is $20.39

https://www.greenmangaming.com/games/destiny-2-the-witch-queen-pc/

Witchqueen has a pretty fun campaign you can play we've done some of it on weekends I assume the free missions that give you a taste of it.

Think you also get some of the witchqueen activities like wellspring but that's just so so

You can get the witchqueen deluxe pack for $45.55 which includes the above as well as the season pass for seasons 16-19 and access to the dungeon and raid as well as the exotic ostio striga (which is a fun poison spreading SMG) but we are currently on season 18 and it's nearly over so not sure if it's worth double the price you can get the bits piecemeal in the game so not sure the extra 20 bucks is worth it at this point

The also have the 30th anniversary pack for 14.23 but that doesn't include much the dares of eternity activity in that is free to play anyway so you're just paying for the dungeon grasp of avarice. Admittedly it's a fun dungeon and one of the very few I've completed (it provides the very powerful Gjallarhorn Exotic Rocket Launcher) but not sure it's worth 15 bucks

They also have a small discount on the upcoming lightfall expansion that comes out next year but not really worth it I suspect

Out of the options available I think the legacy collection offers the best value you get access to all the old weapons some of the older raids and dungeons as well as Stasis and Beyond Light (which has it's own dungeon and raid) which have some pretty good chunks of content.