I am driving on Monday (23rd) from Cambridge to Folkestone/Dover, Calais, Brussels then Wavre (Belgium I'll leave mid-morning, getting on the Eurotunnel around 2pm and will be in Brussels around 6pm.
I have 2 spaces available, and space for luggage. I would ask for a small contribution towards the cost of fuel and the Eurotunnel, depending on how far you want to tag along. Full distance (Cambridge to Brussels) would be £45. Definitely the cheapest way to get there at such short notice!