Yes other sources are available. Bloombergs is a pretty good one if you are looking at markets.
The BBC states "Craig Inches, head of rates and cash at Royal London Asset Management, said the bond market "is largely concerned that a new chancellor will rip up Reeves' fiscal rules and go for excessive unfunded borrowing", along with concerns about UK growth." This is more about Starmer not backing her and uncertainty around whether she will stay or not. Markets aren't too worried about emotions, more hard facts.