I've just been to London this afternoon and the best shop for demo I could find is Shasonic.
They had Grados (SR60i, 80i, 125i, 225i, 325i, RS1), Sennheisers (HD598, 600, 650), Shure (SRH840) & Audio Technicas (AD700, A900, M50) all for demo. It's very hard to find a shop that offers demo of high end headphones in the entire UK. So you can imagine how happy I was to find it.
Only problem is that the salespeople there does not seem to realize how good the gear they have for demo are. I tried chatting with them and they don't seem to know much. Plus, you have to bring your own source! So I had to plug in the HD650 into my Galaxy S, fortunately powerful enough but you could imagine how frustrated I was because I wasn't able to fully test them. I advised them to use a good CD player and amp for the demo units but as I said they couldn't understand that all those gears need proper amping and source! They don't seem to interested in my "advice".
Anyway it could be they don't trust my young looks so maybe an experienced and well aged audiophile can go there and speak to their manager about this?
I went to this shop today thanks to this post, they really have several headphones, as far as I can remember there were boses, sennheisers, grados and then sony. Each brand has 6 (8?) models (may be more if you don't bother asking). They now have good sound outputs with songs that range from classica to pop, anyway I think it's still better to take your on device with the songs of choice . Well the headphones are a little old some of them may not have the sound of a new one as I could make sure with the one I took.
ps.: got a Grado SR80, although a Bose of same price was really attractive, I think if it was not for that *techy* design and a considerable noise I would go for the bose. I don't know much about headphones to be honest.
thanks, that was a priceless advice. In the end I didn't take the time to look for more shops as I just had one morning left in London at that point. There were other shops between tottenham station and this shop that might be worth taking a look for better prices (not sure).
You can try out quite a good selection at Selfridges on Oxford street.
Directions: Get off the tube/underground train at Bond Street station and go left for about 50 metre and the store is opposite.
They have the Sennheiser HD800's which I tried (excellent but cost about £1000), Denons, Ultrasones, and many more.
They are all on display where you can play your ipod or phone etc. through to the headphones.
The staff let me try the HD800's which were not on an open display but in a glass cabinet, due to their cost I expect, on a Marantz CD player and Marantz amplifier that they have set up there, which I'm sure is still an option if you want to use it.
I was only there last week so you can definitely go there and try them.