The CK61 is a very reasonable choice for pub/bar performances: lightweight, compact, quick to start up, good enough piano/EP/organ sounds, intuitive interface, multiple connection ports, easy split/layer, and priced right within your desired £750 range.
The biggest drawback is the smaller-than-standard piano keys, which can feel strange when switching between keyboards, but at this price point, there are almost no other keyboards that are both fully featured, lightweight, and have larger keys. Therefore, the CK61 remains the most suitable choice for your performance needs.