I’m based in Scotland and looking for advice on a domestic scale biomass boiler supplier?

Was going to put one in a garage, so does it need a chimney or can you use a S/S flue.

Go on the green building forum – some very knowledgeable people and help from them. It would need a high temp (vertical) chimney, but can be S/S or pumice – you could not port it out like a gas boiler flue horizontally.

http://www.greenbuildingforum.co.uk/newforum/

Depends how big and how much money you’ve got and how automatic you want it and what you want to burn.
Logs/wood/chippings/pellets/coal etc etc

I run a stove/fire that feeds the hot water and heating and it’s not automatic in any way (other than the pump coming on when the system is up to temperature)

If you’ve got the space and money you really want a boiler into a buffer vessel then you can run as if it’s automatic from the buffer. Obviously you have to manually fill the boiler etc.

SS flue of the correct type for the fuel will be fine.

Get something that produces excess power (and, preferable, combined heat and power), so you can sell it back into the grid via the forthcoming feed-in-tariff to be introduced under the imminent Renewables Obligaiton Order.