There isn't much choice of SL BD-R here in the UK. (Good idea to add your location to your profile, makes it easier to answer. ) It's rather a case of choosing which brand name you want on you Ritek or CMC Magnetics. :sad:
Even formerly reputable brands like Sony & TDK have gone down that route. If you're lucky they're CMC Magnetics (probably second rate stuff, but no degradation horror stories yet). If not they're probably Ritek (past problems with severe degradation, probably solved but do you want to take the risk?), or possibly Moser Baer made MBI or Philips (extremely variable quality). the chances of getting 'real' Sony are very slim.
Recommended reading: http://club.myce.com/f33/bd-r-blank-media-manufacturer-hides-behind-labels-333038/
My best recommendation currently would be Verbatim Datalife (about Â£0.40-0.50 per disc in 50pk). So far these have always been CMC Magnetics BD-R (no reports of Ritek :)) and of good quality. The quality of CMC Magnetics discs varies a lot, but Verbatim (so far) have always had the 'good stuff'.
Annoyingly, in America they get 'real' retail Datalife Plus Verbatims for a better price. :a But here in the UK the only sources of 'real' Verbatims are MABL in jewel cases (expensive) or white-label Datalife Plus like the ones in your link (expensive & hard to find - aimed at the business market).
Last year there I would have recommended Infomedia BD-R. The price was very low (~Â£0.34 per disc in 50pk) and the quality superb (scans almost as good as Panasonics!). Under another brand they have been a favourite of our American members for years, but this was the first time they reached Europe. Unfortunately earlier this year I noticed a note on the distributor's web site saying they were now Ritek discs (not Infomedia's own).
Last year Digistor switched to Panasonic BD-R (blue label 'Professional Grade', made in Japan). These were available from Amazon.co.uk for less than Panasonic BD-R, but I've just checked and they aren't stocked any more. They're still on Digistor's own web site for $1 per disc.
Falcon Media recently ceased production of their BD-R (TDK MID, made under license), but they is still stock available. Here in the UK they have always been extremely hard to find and normally very expensive. The quality is rather variable - sometimes superb scans, but often mediocre with rising errors towards the end. But unless the scans are truly awful they are considered to be a high quality disc and a good bet in the long-term. Riverproaudio.co.uk have some at a very low price for these discs (Â£0.52 per disc in 25pk), but they are not a vendor I would recommend unequivocally. [Approach with caution, make sure you know your rights, stand your ground and be prepared to be lied to.]
A relative newcomer on the market are Optodisc BD-R sold under the Plexdisc brand name. Our American members seem delighted with them - very good quality at a great price, a nice replacement for Infomedia. But here in the UK I have only seen them on Amazon.co.uk at an astronomical price (for Â£1.16 per disc in 25pk I'd rather have Panasonic).
These days I normally buy my blank discs from Amazon.co.uk (or hunt for old stock from the good old days on Ebay). The only specialist vendors I trusted have gone out of business and I haven't had too much trouble returning discs to Amazon which fall below a minimum acceptable standard. If I needed to buy some more BD-R at the moment it would certainly be Verbatim Datalife CMC from Amazon.
But in the last 18 months I've accumulated a stockpile which I hope will last be a while: 200 Infomedia, 125 Panasonic, 50 Falcon & >150 Sony (made in Japan - Panasonic quality at a Ritek price from bankrupt former specialist vendor on Ebay. Grabbed the lot, everyone else preferred to import overpriced CMC & Ritek from Japan!). If I can actually bring myself to use any. (Irreplaceable:sad:)