[Closed] New bag help

I'm in the market for a new bag to take to the Alps with me. It needs to be big enough for full days out and have room for a bladder. I'm also shortly undertaking the Tranpennine challenge and will also need a bag for this. Ideally, i'd like the bag to double up. I don't plan on doing any marathon hikes in future and the walk has rest stops every 25km so essentially will need to fit some snacks, first aid kit and general supplies/clothing changes. I don't really want to have to buy a seperate bag for what will be a one off event.

Anyone got any recommendations in terms of size I should be looking at, make, model etc?

Thanks.