Looking for something at 30L for commuting and dont want it to be a messenger style bag; ideally a rucksack. Seen an Osprey Manta 30L, but think it’s more designed for walking rather than riding.

Look at OMM, inov8 and Raidlight for good products. .

Check out the Deuter Alpine as well.

I recently picked up a Manta 25 (for carrying a DSLR and other kit on longer rides). It’s not as big as a normal 25 litre pack so I would guess the Manta 30 is going to be similar. Despite being designed as a multi-sport pack I find it works well for biking.

Other options in the Osprey line are the Talon 22 and Talon 30 – they don’t come with a bladder (but can take one) and are much roomier than the Manta series as most of the space is in one large compartment.