Thanks for doing this. I appreciate getting such a useful comparison.
It turned out that someone had bought all stock (more than 10) of the B-grade graphics card that was my main reason for going to OcUK, less than 3 hours before I was leaving for the shop. So I never went. I looked locally during my lunch break from work, but there's nothing to be had nearby that I wanted. I could order the DR100s online for £30 including delivery, which seems very cheap, but I dislike having things delivered. Or, more commonly, coming home from work to find a "no-one was in, we couldn't deliver" card on the mat.
I may as well pay ~£35 for the DR100s as opposed to ~£25 for the DR50s. Even if they only last a year, that's about 21p a week difference. I use headphones a lot, so it will defintely be worthwhile.
I did find one very scathing review of the DR100s, with the author wondering if Goldring have changed some important components and describing them as "shrill". I'd link to it, but it's on a site that sells lots of things, so it's probably seen as a competitor.