Good Afternoon mrsd,
The currency in Croatia is Kuna which is widely available in the UK.
Kind Regards,
Mildred
Hi there. If you are going on the day trip to Lublijana, (which is in Slovenia) you will need to take your passport on the trip and also they use Euros there, so perhaps a few Euros for any souvenirs, and some lunch if you want any. 🙂
As Mildred has said Kunas for Croatia are widely available here, but you may find (at least this is my experience9 that you may need to order them a couple of days in advance of your trip.
Have a great time. It's a lovely holiday, a good hotel and an excellent TM. 🙂