NMKC, I agree, there is a risk of further capital falls, although if you are holding to maturity that shouldn't be an issue (except psychologically perhaps). UK yields are indeed the highest since 1998 but they can always go higher.
I don't think RR will resign over it. They will find a way to blame the previous government or some global macro drivers that have absolutely nothing to do with the recent budget, and nothing at all like what happened after the Truss budget.
The bond vigilantes will be sated by spending cuts or further tax rises. The government has insisted that there won't be another budget before next Autumn, so it remains to be seen whether sufficient spending adjustments can be made in the interim period, or if things get so bad that they are forced to raise taxes sooner. Either way, more tax rises are likely, and if inflation is on the up (as is feared) then those rising yields will get eaten away.
Perhaps one question is what all of this does to sterling? The pound has fallen slightly of late, and this may continue, so perhaps US treasuries are a better option? Yields are also rising in the US in advance of the new Trump administration, but a lot may already be in the price, and if the $ remains strong relative to sterling, there is some protection there.
Alternatively one might conclude that lending to governments isn't quite as risk free as it seems (depending on duration and how bonds are held).