Hmmm you might have an unusually shaped toilet, but Brondell makes easy-attach ones - they should be £20-£50 absolutely maximum. They fit any style of toilet, even portable.
You shouldn’t need a plumber unless you’re getting a Japanese, Rolls-Royce level bidet with angled shooters, heated seating, and twirl pattern. It’s really just - turn off water, disconnect hose from toilet, connect bidet hose, connect old hose to bidet hose… water back on. Overall if you’ve ever built something from IKEA, you can probably attach one of these bidets.
But I’m just speaking from preference. Got one during the great TP assassination of 2020 and haven’t looked back since - mostly because I have a sprayer so I don’t have to look back anymore.
That said it’s pretty hard to beat £40 a year price wise - comfort wise though, it’s all down to preference.