are you using the DB site? If not try that for connections. Here is what DB say:Dear customer,Unfortunately, it is not possible to book a bicycle ticket for this trip on the InternetPlease visit a Deutsche Bahn ticket counter or call our service number
Tel.: +49 (0) 1806 99 66 33 (20 ct/call from a German landline, max. 60 ct/call for German mobile phones).
You can request information on bicycle transport, purchase bicycle tickets and make reservations on this number every day from 8 am to 8 pm.
You can book bicycle tickets on the Internet under the following conditions:
Your selected trip:
- only includes trains that allow bicycles,
- doesn't include any night trains,
- only includes domestic routes,
- begins at least one day after the day of the booking.
Go to http://www.bahn.de/i/view/GBR/en/index.shtml
for more details.
You can certainly book a route to the coast that will take a bike. You might find ringing will get you further than using the web - people do manage to get bikes on DB Ice, Thalys and Eurostar services! Koblenz to Koln is easy - I wouldn't try booking as part of the rest as you can probably get a regional ticket price (remember to book your bike!) Currently everything changes at Brussels so you could get either Thalys or the slower stopping service from Koln for that leg and then use Eurostar from there.
You could potentially use the new intercity bus services for part of your journey ADAC Postbus and MeinFernbus both take bikes and the fares are low! Checkout here for details http://www.goeuro.co.uk/search/NTNkOTIw ... kxNTU0OA==
Hope this helps