the extra pound on each part is only if the finish is changing, not just for any gloss part.
for example,
to anno a dust black barrel dust red would be £6, but to anno it gloss red would be £7.
where as to anno a gloss black barrel dust red would be £7, but to anno it gloss red would be £6
that being said, it has been a while since i have checked thier prices so it may have changed