Last winter on a stretch of the Grand Union nr Daventry i found that the Gudgeon would go mad on the inside line (2 or 3mtr whip) by feeding Swim Stim Green groundbait with a pinch of Garlic flavouring and a pinch of 2mm pellets with walnut sized balls feed every 5 mins.
The groundbait was mixed so it would break up about 2inches off the bottom in 3 ft of water and single Flouro Pinkie was the killer on the hook the only problem was that after about 2 hours the Skimmers would move in (but i did not mind).
i think that sensas market a garlic flavoured groundbait additive targeted at gudgeon called picardie, could be worth tracking down or have a look on the sensas website (sorry, don't know the address, but i'm sure that someone on here can help)
Years ago we would never fish a Winter League match on the Yorkshire Ouse without the stuff (especially if the river was in flood)It seems to draw gudgeon from miles around.
It comes in a white paper packet - I'm sure Pete Rambow at Cleveland Angling Centre had some on the shelf last time I was in there. (Sorry Toma but I don't think your wonderful tackle emporium stocks it)