How long before fuel becomes 'unaffordable'

[Scythe13]

If it goes up beyond £1.60/ltr for unleaded, I won't be able to afford it. I'm already considering getting myself a 50cc moped, but splashing out a grand or so upfront for a decent 2nd hand one is another stumbling block.

That's something I've been looking into more recently. Getting a bike. Not so good in the cold/snow/ice. But MUCH more affordable for fuel and the alike.