Why not try our heat calculator - http://calc.fireplace.support - just enter your room dimensions and you will get a good idea. Or pop into our showroom and have a chat with one of our friendly advisors.
In most cases for a gas appliance, as long as the chimney is sound and passes a smoke test, you would not require one. For solid fuel appliances typically any property built prior to 1970 would require a liner. Some manufacturers also recommend using a liner for their product as it can improve efficiency.
Certainly, we work with some of the UK's biggest fireplace manufacturers including Worcestershire Marble, Caterhams, Elgin & Hall, Aurora to name only a few. All of these can make special sizes fireplaces or hearths etc.
No. Fireplaces, fires and solid fuel appliances need to be installed by qualified and experienced technicians who are both trained and registered with the appropriate professional body. Installation by a non-qualified person may invalidate your warranty and house insurance in the event of incident.
For a gas appliance if the gas input is less then 6.9kW then in most cases you would not need an air vent. For solid fuel appliances, typically if the output is 5kW or less then you would not need any air vent, although there are some exceptions for newer properties and for some appliances.
This varies from manufacturer to manufacturer and ranges from 1 to 25 years dependant on manufacturer. Each manufacturer has their own terms and conditions and it may require certain parts changing each year, appliance servicing, and the guarantee may be parts only after a set time. Please see manufacturers terms and conditions for further details.
If you are looking for efficiency and a saving on your gas bill then glass fronted would be best. However, they do cost a little more in the first place and so if you aren't using the fire that often you may never recoup the cost and so an open fronted fire may be best. Aesthetically, most people prefer open fronted as there is no reflection from the glass.
The type of chimney you have will determine what appliances will be suitable. Typically class 1 chimneys mean you can have any appliance where as class 2 (pre-fabricated / pre-cast flues) mean there will be less choice. Most manufacturers make the type of chimney required very clear in their brochure.