http://www.germany.travel/en/leisure-and-recreation/cycling/ruhr-valley-cycle-route.html.

http://www.ruhrtalradweg.de/Strecke

Staying in Hotels (or Youth Hostels where practical).

Allow £30 or possibly a bit more per night average for accommodation

Allow 6 days to include a bit of sightseeing (or possibly a day or two more for extensions).  Total accomodation costs: allow £200

Provisional Itinerary

Day 1 Winterberg to Arnsberg

Day 2 Arnsberg to Frondenberg

Day 3 Frondenberg to Witten

Day 4 Witten to Ketwig

Day 5 Ketwig to Druisberg

Possible extensions

More details to follow.

Getting There

Best option is to take overnight ferry to Holland (cost: around £120 if we have 4 people in 4-bed cabins) and then train from Hoek (soon to be part of Rotterdam Metro) to Winterberg for start of ride and return buy catching train from Duisberg to Hoek (advance purchase tickets - allow an extra 80 Euros total for these train tickets.) Buy tickets (with Bike reservations) from German Railways website.  

Total travel costs from London (including bike transport): allow £200