Medium size but must have a main strap with quick release and at least one outside pocket for phone and wallet. Preferably light, well made, fairly bright and visible, made in UK (no chance I guess), fairly sustainable materials.
Ta
Have a look at the Osprey Flapjack. I use one for commuting (easily holds a laptop plus sarnies etc). Outside pocket is on the end but easily accesible. Not made in the UK though...
I got mine (in black) from:
http://www.tauntonleisure.com/osprey-flap-jack-courier-pepper/p6641
Personally I think the black looks best but take your point re visibility!
bagaboo (Hungary)
I can thoroughly recommend Chrome bags: http://www.chromebagsstore.com/bags.html
My Metropolis is still going strong 7 years later.
http://www.chainreactioncycles.com/Models.aspx?ModelID=3251
i got a big banjo bros (terrible name..) bag which is great - the quick release requires unweighting the bag to tighten if there's anything in it.
it's been waterproof in everything i've ridden in, useful pockets and is pretty cheap - here's a medium version http://www.urbanhunter.biz/acatalog/Banjo_Brothers_Medium_Bike_Messenger_Bag.html
I like my Timbuk2 bag. Mine is a classic, medium size. I've had mine for years, still in good condition, and waterproof enough.
Available in loads of colours/fabrics etc. The custom ones are made in San Francisco, standard bags are made in China/Philippines etc.
Second for the Chrome bags. Beautifully made and rugged, waterproof and look cool to boot. Not cheap but you pays yer money. I just wish there were bags like this available when I was a bike courier in the Smoke.
My Osprey flapjack is great - I run it with a longer strap so it sits on my lower back.
My metropolis is across the top of my back whatever, and is a lot more sweaty. Possibly stabler at carrying loads though.
got an osprey talon
it is good , not too big , good laptop protection
bit small for me now though. It will fulfill your requirements though
narrowed it down to a timbuk2 classic messenger in large i reckon as a bike bag and a carry on bag - those of you with this bag is it too big for a carry on bag really ?
What about the new Ortleib bags - they are waterprrof and come in diff. flavors?
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Another recommendation for [url= http://bagaboo.hu/ ]Bagaboo[/url] here. GReat custom options and my bag is proving very durable too.
Bagaboo. I have used mine day in, day out for the last 5 years and its still holdng up.
No one said Crumpler? my Wonder Weenie is 15 years old now and still looks in good shape used all the time.
i have 2 timbuk2 medium classic courier bags and they are brilliant. one is 15 years old and looks as good as the day i brought it. nothing has ever got wet inside them even in the worst rain. am looking to get another large one in the not too distant future.
oh, trakke based in glasgow too, i've seen them in the flesh, very impressed http://www.trakke.co.uk/