WCSB

Nowhere near that size, Pete. My estimate would be about 1" to 1.25" body length. Still quite a lot bigger than our shield bugs.

Got the photo Neil, but I did google it too. It said it was 3 to 4 inches long! I bet you got a shock when that trundled across your carpet.

...... Pete

I have now managed to attach a pic of the bug in my original post. See below.

Hi Pete. I read that they had spread eastwards across North America over time and had been recorded in UK since 2007. I had stored an oil-filled radiator in my lock-up garage, in
its original packaging box since the end of last winter. I donated it to my daughter who lives a few doors away from me and after sliding it out of the box a creepy-crawly caught my eye, 
It was very lethargic as it made its way across the living room carpet. At first I thought it was a shield bug, but couldn't find anything like it in my wildlife guides. It was much bigger and longer.
I took some pics on my iphone and iNaturalist Seek app identified it as a WCSB. It looked absolutely spot on, so I posted it on here but unfortunately it didn't download my photo. An impressive little beastie!

That's amazing, these are native to North America but are spreading. Did it come in a parcel?

Western Conifer Seed Bug crawled out of cardboard box in my garage in Cleethorpes today. Huge in comparison to usual shield bugs.