I think I know the answer, but...

The crack is about half way down the seat tube, it's 2-3cm long and I can feel the metal around it give to a gentle prod. No idea how it happened.
Frame is a Voodoo Bizango, aluminium, a bit under 2 years old and not in warranty. Halfords will replace it for £120, +£80 if I want them to swap everything over. For the money I'm thinking I'd be better off finding a nice 2nd hand frame instead, but is repair an option?
Not worth repairing and definately dead.
I'd look for a parkwood as most parts will port over and should get a frame for 50-60 quid.
Repairable? Yes
Worth doing? No. Unless you are particularly attached to it and happy to spend way more than the cost of replacement.
Oooof, yep - sorry, but that’s a goner.
I did a random similar thing years ago with a genesis core frame. I had a comedy slow speed off where I went half over the bars before the back end of the bike flopped sideways onto rocks and roots. It cracked the seatstay right in the middle of the tube.
One of those things - a riding accident.
WRap a coke can round it and then cover the thing in jubilee clips, see how long it lasts. You must report back though...
RIP
Thanks for the responses.
I changed the wheels a while back and can get an adaptor kit for the rear to fit most non-boost frames, so I should have plenty of options to choose from.
Parkwood is a good shout, or another bizango. Depending on use, inbred or scandal frame too. Plenty similar out there. Happy hunting.
Where are you located?
Why wont they replace it? If it's under two years old it's still in warranty. I'd go and try again and explain that you'd expect a frame to last more than 2 years!
There’s a L Parkwood 650b frame sitting in my garage I’ve been meaning to get round to selling if you’re interested.
Where are you located?
Kent
Why wont they replace it? If it’s under two years old it’s still in warranty. I’d go and try again and explain that you’d expect a frame to last more than 2 years!
Me too but they only offer a 1 year warranty. It's not something I thought about when I bought the bike and it does look like impact damage so doesn't seem worth making a fuss about - I can't really claim it was defective when I bought it.
There’s a L Parkwood 650b frame sitting in my garage I’ve been meaning to get round to selling if you’re interested.
Thanks but it's a 29er. I'll keep an eye on the classifieds and see what turns up, I'm not sure I want to replace it like for like anyway.
No, it's resting.
Voodoos warranty is 2 years-Halfords are spinning you a yarn.
It could be worthwhile contacting Voodoo directly if Halfords are being rubbish.
It will be worth chasing up the warranty but if that fails and you can get it up to Peterborough I can fix that for you. It’s on the seat tube so if it does go again it shouldn’t be catastrophic.