You can ask for a 12 month lease with a six month break clause, which would allow you to give notice at month 4 to move at month 6, or two months notice any time after that. It protects you from further increases for 12 months, so I would go for that.
Rents have slightly fallen in my area too, so I understand asking for 6% more feels like a piss take. I wouldn't be happy if my LL did the same. Probably to cover increased mortgage, maintenance and insurance costs, I imagine.
Ask yourself though, would it cost you more than 6% x 12 to move? Every time we move, we have to pay for a ton of new stuff. Curtain rails, curtains, quite often a fridge, freezer, cooker, washing machine and dishwasher. Plus removals. It's always a few thousand pounds, without fail. 5k for the last two moves, in fact.
I think it's a bit different in towns where these things seem to be provided as standard. But most countryside LL's just don't.
Doesn't matter if they should have given you more notice, really, does it? If they want more rent and you quibble over how much notice they've given, they'll just issued a section 21 and get you out.
I would see it as a negotiating point and see if you can get them down a bit. Or just suck it up on the basis that it will be cheaper and less stress than moving home again.