Firstly, you won't get a 6Kg Calorlite anywhere (save old stock - and that's unlikely as they were always in short supply!), they were discontinued in Feb.
If you don't already have a Calor cylinder, or are prepared to pay for the rental charge (or can find a s/h cylinder), Flowgas are an alternative supplier with generally a much better reliability of supply. But check cylinders will fit, they differ slightly from Calor's sizes. https://www.flogas.co.uk/shop/category/all-cylinders
You won't get Calorlite, but a couple of times we've managed to get Calor propane from Lakeland Aggregates, Canal Street, Ulverston (at the top of the cattle market by the car wash).
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets