Hi, I'm brand new to the forum!
I have an Audi Quattro TT 180 BHP 1.8 2003. 75000 miles.
A few weeks ago I noticed what I can only explain as a slight clunking/knocking sound coming from under the front footwell which I could feel and slightly hear. This seems to have got louder and can feel it more over the last couple of weeks. You cannot feel or hear anything on standstill, it seems most prominent when driving at around 25-40 MPH and it doesn't make any difference when turning, simply when driving. The noise and feel gains momentum with speed (as though it is something to do with the rotation of the wheels going round). I had the car MOT'd and an interim service 4 weeks ago and no problems were found (I had asked the mechanic to check out what this noise could be but he found nothing). I don't know whether it is connected but 3 days ago a warning light appeared (a red exclamation mark within a circle and brackets) which comes on at random times then disappears. I have looked this up and it states something in regards to 'brake failure'. I have no problems with the brakes and nothing was flagged up at the MOT. I'm looking for advice as I've read through quite a few posts on here and it seems a garage may try several things with no luck in finding the problem so I just want to try and narrow it down before I start spending!
Could you offer any advice as to what the problem could be?

p.s. I purchase the car in January and the previous owner provided me with receipts showing that within the last 12 months he had a new cambelt fitted, replaced breather hose and ribbed belt, new outer CV boot, new lower arm bushes, sump repair, new rear anti roll bar, new oil and filter, gearbox oil change and new battery.

Many thanks in advance!
zoe