Where can I buy this stroller, please? I can’t seem to find it on any UK website.
I am sorry, but unfortunately, the Crosster Flex Signature as well as the Joie Crosster are discontinued already, so they are not available in online stores anymore (if so, then only as the last "old" pieces). The manufacturer didn't say if they will be produced again (which is a shame, as it was a very reliable model, actually).
I would suggest checking any classifieds or eBay if truly insisting on this model.