If all fails with sourcing MR 16, would it be possible to disconnect the transformer and re-wire in 230V and replace the bulb holder with GU10?
You may find a wider choice of beam widths and outputs etc in LED GU10.

Thanks for the thoughts.. I do kinda like the rewire for a 240v GU10 idea. Presumably, that would be as simple as taking the +/ - 240 directly to the GU10 holder?

As for the bulb holder itself, there is only the ceramic base with the two wires, not actually fixed to anything, just floating. The bulb is kept in place by a C shaped spring around the edge circumference.

A for the number on the bulb, only listing what is printed. The brightness is not so important as the light only runs for three mins as a default when the door is opened or closed. It is not a garage illuminating light.

May be a silly ask but.....

I have inadvertently ordered and had delivered a 240v LED MR16 rather than what I though I was ordering, a 12v.

Given Owlman's suggestion above, is there any reason that I should not by-pass the transformer and just attach the 240v wires directly to the existing MR16 bulb holder? Would both wires and holder be designed to handle 240v?

240 V is a lot more dangerous than 12 V and you will need to check that where it is mounted complies with the relevant safety laws.

As the existing is halogen then the chances are you'll need a new LED driver. if you want to stick with 12V.
If you want to ditch 12V in favour of mains then best to go GU10.
I can't remember where I once read about mains MR16 not being compliant. It may well be OK; I'm guessing here but it may also be something to do with the flimsy pin connectors, the twist and lock GU10 being more secure for mains usage .

@ Peter;
OK, compliant was maybe the wrong word. Rex inadvertently bought an MR16 reflector with a GU5.3 base instead of a GU10 base.
I was attempting to answer whether a GU5.3 base is permissible for mains voltage in general household use, as opposed to factory fitted specific equipment, which can be the case.
Possibly this may lead to confusion and people replacing 12V GU5.3s reflectors with mains voltage ones and vice versa. Hence the GU10 base being the more usual mains voltage option.
I don't know if this is the case just surmising.

Posted By: RexSeems the best option is to buy a GU10 base and wire it directly to the incoming mains. My guess is that the motor itself operates from a transformer.

Depends whether mains is fed to the unit and the voltage reduced by a transformer inside it, or whether the voltage is reduced by a wall wart and only 12 V is supplied to the opener.

Whilst in a meditative moment, I realise that it is not possible to go with a 240v GU10 bulb. When I open the garage door, the light activates for around 3 minutes and automatically switches off. Any bulb that by-passes the electronics will not do that and most likely will turn on but not off.

But I have found this which does tick one box, that of a wider beam angle.

https://www.amazon.co.uk/Spotlight-Generation-Equivalent-Halogen-Dimmable/dp/B07J5TJ1S2/ref=sr_1_42?keywords=MR16%2BBulb&qid=1702923211&sr=8-42&th=1

Given what I have read that I need an LED that says 'the equivalent of' and this exceed the halogen of 35W, is this likely to work flicker free? Although it does say it needs a LED transformer and I don't imagine it is possible to wire one into the motor housing so that it does give the 3 minutes.