Just caught your post.
There IS a solution to remove and help prevent it coming back.
Take a look at
http://www.originaltouch.co.uk

Step 1 - Apply Batiface for removal of all moss, algae and mildew,
renovating the surface to 'as new' (leaves tarmac black)

Step 2 - either apply Batimoss (a fungicide) or Hydromoss (a water
repellant sealant)

It works really well and we have had no greening on our drive for the
last 5 months over the very wet winter
(But do apply in dry weather!)

Hope this helps

Sam