Just started commuting by bike and need a decent waterproof bag that can hold work clothes, laptop, lunch etc.

Lots of pockets and a flattish bit for shirts

Any recommendations, or is the ortlieb thing with the roll top best? Quite fancy a courier style though for use in the train as well?

I’ve got a over-board waterproof rucksack that I use for commuting occasionally. One of these. It’s very good and 100% waterproof.

Not really got lots of pockets though, one internal and 2 external.

I use the cheap Alpkit Gourdon one.
Has no pockets or anything at all inside, but that’s never seemed to be an issue?
Just put the laptop against your back.

They’re only about £25

It might be worth considering something like a Carradice saddlebag as it gets the weight off your back and stops you getting super sweaty.
Combined with a SQR seatpost mount you just end up with a small plastic block on the seatpost when not in use.
I can get my lunch, bike tools, change of clothes and a 13″ laptop in mine.

I have a Dakine pack and its bombproof, dosent seem to be available anymore though. Was reviewed in the mag years ago.

This looks like it might fit the bill

http://www.ewetsuits.com/acatalog/messenger-dry-bag.html

They also have a regular backpack type thing, no pockets in that though.