Eurostar has changed it's bike policy - now they only let folding bikes on board, not full size ones in bike bags like they used to. You can send your bike as baggage, £30 a pop to be on your train, £25 for going on a train within 24hours.
Sad news from someone who regularly used to take a bagged bike on the Eurostar
I traveled to Paris last weekend with my bike, took the wheels off and put the whole lot in a laundry bag on the luggage racks. Absolutely fine both ways.
I went to Brussels on Saturday and at St Pancras there were signs saying bikes in bags were fine!
I went to Brussels on Saturday and at St Pancras there were signs saying bikes in bags were fine!