Thought I'd post this incase anyone else experiences the same issue.
Last night my S3 started spluttering under full throttle & engine warning light flashed yellow.
I took it to the garage today & it was diagnosed as having a faulty ignition coil. The mechanic said the other 3 were ok but his experience of the mapped S3's showed that some can also follow shortly afterwards.... Because of this I made the codtly decision to change all 4 so im £300 lighter today (Birthday too). The price is diagnostic, parts, VAT + labour.
Next month I can look forward to a full service, plugs, brake fluid & the Haldex oil needing to be serviced due to being at 40,000 miles.
S3's are fast as f*** and loads of fun but Jesus they kick you in the ********....HARD!!