wrote in message
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Looking at oil fired combi boilers, preferably external boxes.

House does not have a header tank uses afortic tank on a very old
rayburn at present.

I have so far found two possibilities:

One from Grant, (http://www.a-b-d.co.uk/Grant/Grantoutdooropt.htm,
http://www.grantuk.com/)
and the other from
Turco (http://www.thermsaver.co.uk/turco/boilers.html).

The Grant uses a Riello burner which seems to ber rated Ok.

Try taking a look at Firebird Boilers. They make an outdoor model oil fired
combi