There's a list here...
http://www.homeheatingguide.co.uk/efficiency-tables.php
it shows about 40 different Spacesaver models and they're all band G and attract the scrappage allowance.
Boiler must be working (how would they know?) unless you're over 60 and the scheme does not operate in Wales. You get the £400 allowance only after the completion of the work but you have to apply before it begins I believe.
More here...
http://www.energysavingtrust.org.uk/Home-improvements-and-products/Heating-and-hot-water/Boiler-Scrappage-Scheme
Good luck...
Peccavi
February 2010