There's a list of boilers here - by manufacturer...
http://www.homeheatingguide.co.uk/efficiency-tables.php
You may need to look under
Baxi Potterton
Potterton
Potterton International Heating
Potterton Myson
I think 38-44kW means a power rating in Kilo-Watts rather than a model number
Peccavi
January 2010