There are loads of decent cycle routes in The Netherlands. The long distance national routes, known as
LF routes, are well signed and can be linked together to give plenty of long distance touring options. Generally these are on tarmac, either along cyclepaths or quiet roads. They're better than Sustrans routes because generally they follow sensible routes without silly pointless loops. Occasionally they'll be bits 'n' bobs that aren't tarmaced, but I've never felt unhappy on 23cc tyres. If the sections are untarmaced then I've found the tracks to be compacted tracks, so nothing too horrible and certainly better than some London roads. There's also a load of useful local cycle routes.
Personally, I'd probably chose to head across the centre of the Netherlands because I feel there's more variety in the scenery. Day 1 you could go to Utretch, and then towards Apeldoorn. I'm biased having spent a lot of time in the reedlands, but I would recommend following the
LF3 from Kampen to Heerenveen. Parts of that area are like a waterworld and it feels like boats are the only sensible way to get around. It's very beautiful. From Heerenveen you could then head eastwards to Groningen.
I can also email you some scans of an overview map of The Netherlands that shows the long distance routes, if you'd like?
I've no idea about accommodation.