Ady, assuming you have a road-going bicycle of some kind already, I would opt not to buy an exercise-bike as such, but a turbo trainer.

Turbo trainers take up less space, allow you to use your own bike (that you are used to and comfortable with) on it and generally provide a much smoother ride with more realistic resistance than a lot of the dedicated exercise bikes at the lower end of the food chain.

I own this one: https://www.cyclestore.co.uk/kinetic_road_machine_2_0_smart_trainer-ID_73443

but less expensive and perfectly competent ones are available, e.g. https://www.wiggle.co.uk/lifeline-tt-02-fluid-trainer/

In case you're wondering, I used to race competitively in a club, and had done for over thirty years, until an immune disorder (that developed a few years ago) confined me to slightly more sedate riding. But I still use my trainer quite a bit.

Done a fair amount of Road cycling myself, still get out with the local club when time allows, but never got on with the turbo, would rather flaggelate myself with rusty barbed wire, which im sure would be less painful.