UKC

I've got a £100 amazon voucher (I know, support your local and all, I didn't ask for the voucher I promise!) and looking for a 30L ish backpack for long scrambling/mountain trad route days with big walk ins. Something that holds a rope at the top, maybe some storage for snacks in the shoulder/waist straps, ventilated back that stills lets you move around while climbing. Looking at the Montane trailblazer 30L but wondered if anyone had some other recommendations, Cheers

Various recent options reviewed here:

https://www.ukclimbing.com/gear/rucksacks/small/

And still some suitable among these reviews:

https://www.ukclimbing.com/gear/rucksacks/medium/

I have various Montane Trailblazers (8, 18, 30) which I use for longer running events (18 = single day, 30 = mountain marathon [carrying test, sleeping bag etc.]).  They're brilliant bags for running, but I wouldn't recommend them for climbing and/or carrying a trad rack and a rope.  They're very light because they're built of light (and thin) material - I would have doubt about their robustness as a crag sack.

I know this doesn't help with your Amazon voucher, but have you considered Decathlon? e.g.

https://www.decathlon.co.uk/p/mountaineering-backpack-33-litres-alpinism-33...

Oh this is very useful thanks! I tried to have a look on the website but missed that big review of medium backpacks so cheers for the heads up 

Good intel on the trailblazer thank you! Bit of a shame to hear though as the back and shoulder strap pockets looked like exactly what I was after.

That one from decathlon does look pretty good, probably worth me just heading in and trying some on. 

Amazon have still got the Montane Medusa 32 for sale - I've had one for over 10 years, and apart from one of the clips (which broke a couple of weeks ago), it's still in good nick. I've used it for the sort of thing you've described, as well as long days skiing and mountain biking.

UKC did a review: https://www.ukclimbing.com/gear/rucksacks/medium/montane_medusa_32_rucksack...

Dan does seem to have reviewed recently a number of climber's packs with race vest inspired shoulder straps with pockets, that do sound just like what you're looking for. I'm fond of my Exped https://www.ukclimbing.com/gear/rucksacks/medium/exped_black_ice_30_pack-14... but it is a bit old school with no pockets on the straps which I've found handy on other packs I have.

Another vote of confidence for the medusa - I got one off vinted a few months ago and absolutely love it. I would strongly recommend. It's got all the features you're looking for I'm pretty sure.

Not a ventilated back, but a KarrimorSF Sabre30 is excellent - it's essentially a modern Karrimor Hot Rock 30. Tough, simple, good value for money. I use mine for mountain walking and VFs in the Alps.

https://karrimorsf.com/product/sabre-30/