Did you buy your Greenstar recently? I'm leaning in favour of one of
these
(other option was a Glowworm 30SXi) & best price I can find on it so far
is
£724 inc del.(619 ex-vat) before flue, from discount heating.

I bought it about a year ago, from www.discountedheating.co.uk. It was about
750 quid including VAT back then, but included a non-optional horizontal
flue, so the price has effectively risen a little. In my case, I only used
the turret adapter from the horizontal flue and had to buy a vertical flue
terminal, elbow and extension pieces separately.

Christian.