Sending parcels to the UK pre Brexit was relatively easy. You just took your parcel to the post office and they’d sent it for you. This is apart from things with lithium-ion batteries inside. This is a nuisance for mobile phones, laptops, and watches. An Post will not accept these.
The workaround pre-Brexit was to use parcel motel, tick the lithium battery box and they’d send by ferry. They have temporarily suspended deliveries to the UK though, so it’s not an option.
If you go to a parcel broker site suck as parcel2go.com, then they won’t accept the parcel if you put its a mobile phone or anything with a lithium battery in it.
So, how do you do it? I ended up going direct to UPS.com and sending via there. You can select has a lithium battery in it and as long as it’s labeled right, they will accept it. It cost me €37.12 for UPS Express Saver to send a mobile phone to the UK. It was supposed to be next day delivery but it got held up in customs.
When you book the parcel, make a note of everything they ask for and make sure it’s attached. It got delayed going out due to incorrect paperwork and got delay again in the UK. It’s just not worth buying anything from the UK with a battery in it anymore due to the hassle of returning it. The exception is from Amazon who will sort out the returns for you.