Well. Britain looks like a laboratory for neo-Reaganite economic policy but without the dollar. In fact, if announcing your budget causes yields to rise and your currency to slump, you're more of an EM.
And not sure whether anything will come to Sterling's aid, given rubbish macro trends.
This will obviously increase imported inflation and put further pressure on MPC to tighten, with pretty calamitous consequences, especially for near-destitute households and heavily mortgaged homeowners.
Funny how this is nearly 30 years to the day after Black Wednesday. Sterling/Dollar and even Euro parity isn't that farfetched anymore.