Hello,
The cupholders are around $71 on US ebay, but you need to check with the seller that they'll ship to the UK. I am still wanting to change all my badges to Cadillac badges, and have looked on US ebay, emailed a couple of people breaking (parting out) cateras, but the badges have usually gone.
I tried the cadillac owners forum, but to no avail.
There are a few US GM suppliers that will supply a range of Cadillac script badges and the crest/wreath badge for a reasonable price.
Another option I have been thinking of, is the change your catera to an Omega option, ie shipping my VX badges to the US, so some mad soul can glue them onto his or her catera, and give me their badges in exchange.
To make the grille fit, you need to cut the bottom part off, as the US bumpers are different and nicer looking IMHO.
JCT