Lindsey You do not mention unless I missed it what European countries you are planning to visit.
I was in same position as you where for reasons did not want to go down the refillable route.
I managed to get German bottles and Spanish ones all 11kg. Propane
A lot of motorhomes of European manufacture will tale 1kg but not the uk ( calor )13kg size.
Got mine off ebay and gumtreee like these but not sure what these are
Propane gas bottle | eBay
and
Gas Bottle (empty) complete with regulator valve and pipe | eBay
I will get Le clerc or intermarche bottles when we next visit France, again 11kg
If you fit a 30mbar bulkhead regulator and a pigtail with the 28mm LH thread on end then you can just fit adaptors to this to fit most bottles abroad. I have a hand wheel type for uk calor fitted on the end of this for no spanner uk change overs
Recent prices if interested Repsol ( spain ) 11kg 12euro and Germany same size 37euro.
If you were going in the summer and was not going to use any heating I would say do not worry about it and just take two 6kg callor as we went nearly tree weeks on one 11kg
without using heating and we never hook up. But I know when we do Scotland and heating is needed 6kg lasts 3 days max.
As you mentioned you can carry a full uk bottle and change to foreign one as soon as poss and just use this whilst other is empty.
Gas it and Gaslow selll the adaptors and pigtails
LT Man