For some reason the blickymaker will not handle it, but here is the url for the official BT (UK) speed test. It is the one that your ISP will probably tell you to use if you are arguing with the ISP about your speed.

It can however be clunky and I have found it best to run the test (after following their instructions) before going to bed and to come down to find the result in the morning!

BT Speed Test (click)
Link by Joe Offer Enterprises, Ltd.