Is there an adaptor/extender for a plug socket?

You can get various combined timer/socket units for outdoor use :

https://ie.farnell.com/bg-electrical/wp23tm24-01/ip66-timer-controlled-skt-outdoor/dp/3458819

The issue with that is you won't be able to close the lid on the socket with the timer plugged in. They're not weather proof unless the lid is closed fully.

With lid open, it's just a normal socket.

That's why they can't really be used with Christmas lights that have transformer plugs etc and you have to get weather proof boxes to hold that stuff.

If the 'outdoor room' is within the range of your house wi-fi, you should buy a smart plug, will save you fiddling with the pegs on that timer socket. You'll be able to control the socket from anywhere, using an app on your phone or tablet.

Be sure to buy one with the 'energy monitor' feature, this allows you to track how much power is being used, it only costs about one euro more than the basic model….

https://powercity.ie/product/82425

https://www.harveynorman.ie/computing/connected-home-en/all-connected-home/tp-link-tapo-mini-smart-wi-fi-socket.html

As it's inside and not exposed to the elements perhaps a standard adapter would do the job

Google the following DFE 028020 it will give you an idea of what I'm talking about (tried to link it but it didn't work)

OP, it's probably too late to change the thread title but the two posts above this one shows that there's a bit of confusion as to what exactly it is you're looking for.

The thread title say you're looking for an adapter/extender but in the first post, you say it's a timer you're looking for 😯

https://www.screwfix.ie/p/british-general-900-series-13a-2-gang-sp-switched-smart-socket-white/827GV?gclsrc=aw.ds&gad_source=1&gad_campaignid=20416181191&gbraid=0AAAAADmaied-Chqc1zyMv--VipDJPDfup&gclid=Cj0KCQjwiqbBBhCAARIsAJSfZkZewSB5xPUFg_U2utfxVsR7nkUtthDbm7gbZ57SQNdDk-oIPr0hkNEaAnrIEALw_wcB

^^^^

https://www.screwfix.ie/p/british-general-900-series-13a-2-gang-sp-switched-smart-socket-white/827GV