The UK has been in Ukraine since 2015, on an op called OP ORBITAL - we've trained them, and bought huge quantities of rifles, ammunition, CBRN gear, GPS and communications gear for them.
In addition we've provided them with around 2500 of our own anti-tank weapons from our war stocks and used our people in Ukraine to train them on how to use them - and we did so before the war started, meaning they weren't just dumped at the border with Ukr having little ability to move them to where they needed to be.
The UK provided, for years regular and persistent signals and radar intelligence gathering, both above Ukr in the form of RC-135 and Sentinel, and SIGINT on the ground.
The UK did, with the US, the public warnings that Russia was going to invade.