Timing belt wouldn’t require an oil change. Doubling up on checks is a potential double charge and some garages recognise this by offering a special price when service and mot are done at the same time. If it’s concern shop around.

My indie used to offer a special price but no longer. I take the view that he is still good value for the work done and care taken so I’ve stuck with him.

I may be out of date (quite likely :-) ) but in principle there is little overlap between a 'service' and a MoT. The MoT test is to check that essential things work correctly and show no signs of imminent deterioration. Testers are not allowed to dismantle or open containers etc. (tho a friendly one may top something up). Basic servicing according to schedule will include fluid changes or top-ups, filters and cambelts.

Because there is only slight overlap, it can make sense to do both together, but the MpT is annual, which may not fit the service schedule.

Having just had a service, mot and timing belt change done at a main dealer got me thinking. Aren’t I effectively paying for a number of things twice?.......

Yes.

...For example the oil change would form part of the service and the timing belt change.

Not a good example - thiis is not covered in the MoT, which is purely an inspection for safety and roadworthiness.

The safety checks performed during the service would also be done as part of the mot. Not sure what I can do about it other than staggering the mot and service?

What I did about it decades ago was to dispense with a garage 'service' and just pay for an MoT. You are right in that the MoT checks are the same as those done during the 'service'. Indeed, they are probably done more rigorously as the UK system, unlike more enlightened jurisdictions, has an innate conflict of interest, i.e. if you use the same garage for the MoT and the 'service', it is in the garage's interest to find as much work as possible to do. Hence the advice to build a relationship with a good local 'indy'. For a low mileage driver, the most economical way of caring for the car is to change the oil every 10,000 miles and replace other things when the MoT check or the hand book (there is usually a 'maintenance' section) advises they might be at or nearing the end of their life, e.g. spark plugs, brake pads, brake discs.

However, the trade has got wise to this and encourages punters to sign up for new car warranties way beyond the usual three years or so - sometimes up to ten years, thus trapping them into an expensive annual 'service' no matter how few the miles covered since the last one.