Got it.
That's important to know. I'm going to second several titles that have been mentioned already. All of these appear to be available from
amazon.co.uk, so hopefully that helps ensure some level of availability.
Akira - A cyberpunk classic renown for Otomo's amazing art style, which combines big epic splash pages and a cinematic feel with intricate background detail. In the near future, a bike gang finds themselves involved with secret government programs invovling psychic powers. Things quickly get apocalyptic from there. The whole series has been collected in six oversized volumes, and while they're not what you would call cheap they're a reasonable price for the money and are a reasonable length to collect.
Eden - Post-apocalyptic cyberpunk SF that was quite influenced by Akira; the artist has the same touch for intricate detail. If your brother likes gore, let me tell you, this story will provide what he's looking for. The violence in this is detailed and astonishing, while not being utterly gratuitous. Meanwhile, the plot is engaging, the action is intense, and the story is really, really bleak. It's extremely good. This is an ongoing series, with nine volumes available and about as many to go; this is a tad long, but there aren't so many out that it's impossible to catch up and it really is an amazing series. A note about Eden: the first volume provides a lot of set up, and then things really get going over the next couple; if you can hand him the first four volumes, that provides a fair amount of closer for the opening story arc.
Hellsing - Of course, if your brother is a fan of Hellsing, why not get him the comic? As the TV adaptation wasn't so hot and the more faithful OVA version was only 3 volumes, handing him the original manga isn't redundant. It's got badass vampires armed with guns shooting the hell out of other, lesser critters with all manner of light-hearted gore thrown in. It's hard to go wrong. Eight volumes and going.
Death Note - Finally, something a touch (but only a touch) more cerebral. Death Note is about a teenager who one day finds a notebook dropped by a God of Death. When someone's full real name is written into the Death Note, they with either die in the manner specified if possible or have a heart attack. Our protagonist tests the book on a convicted felon, contemplates what he has in his hands, and then decides to mold the world in his image. Cue criminals dying like flies as the police try to catch him. Despite not being particularly action packed - though the art is excellent and imparts as much excitement into watching someone write a name down as you can possibly imagine - the concept is intriguing as all hell and it's a lot of fun. Death Note is cheap and, at "only" twelve volumes, not overly long. If you want to hand your brother a nice big stack of manga, here's the best way to do it.
And that should give you a good start. Again, hopefully most of these titles are readily available where you are. Let us know what you pick out for your brother!
FnordChan