I have recently replaced the motor on my 2008 Pro Connect with a 2011 motor supplied by Martin at e-bikeshop. Martin is very helpful and a fair chap to deal with so definitely worth talking to.
I didn't approach 50 Cycles, but £500 for a motor raises the question as to whether it is economically viable to repair the bike. If you are still using your original battery, you must factor in the possibility of replacing that any time soon too. Having said that, my 2008 batteries are still going strong.
I have seen motors on eBay for around £350 from Germany, but they are rare and you need to keep looking. Also Pro Golla are worth keeping an eye on.
http://www.pro-cycling-golla.de/suche.php?seiten_id=3&suchbegriff=Panasonic&extendedSearch=1&order_type=name&order_direction=ASC
Prices tend to vary and he 26 volt unit is currently showing out of stock and a price of 500 Euros. This does tend to go up and down though.
Member d8vh did have a 36 volt motor and battery for sale from his damaged BH bike. The motor mounting is the same as the 26 volt, but I don't know if the battery frame lock is the same or if the 36 volt battery connection dock will fit your bike. Logic says it should, but that needs confirming.
It's worth hanging on until the right deal comes along.