we are moving to a house without a chimney and I want to put in an LPG gas fire - what do I need to consider and what is a rough cost

you can only fit a fluless gas fire into a property with no flue and needs to have permanent ventilation cost is about £900.00 supplied and fitted for natural gas,not sure about lpg models.

If there is no flue you could consider installing a twin wall insulated system - designed to be fitted where no existing flue is available. Can be mounted internally or externally. This would then open up any appliance you liked the look of rather than just being restricted to flueless.