Paul's was a 2009 and had 120s... so it looks like the spec changed during the year. I think they could be changed from 80 to 120 by swapping a spacer but had to be dissembled to do it.
100mm on my 2010, but they seem to change spec mid year because I met someone else with the same bike and my reba's have blackbox motion control and theirs doesnt.
Based on my research it seems
a) it depends on which batch your '09 model 'year' comes from clearly some HT's got forks intended for FS bikes which were spec'ed at 120mm
b) some Boardman, and other, OEM Reba's can have different internals to after market ones and thus may not allow for the spacers to be swapped
c) some Boardman, and other, OEM Reba's aren't OEM Reba's at all but aftermarket (?"All Travel"?) models shipped to the manufacturers
I get the impression that Boardman were basically fitting whatever model of fork they could get their hands on, such was the deserved success of the HT range.
Based on one short test ride of a HT Pro with modded Reba Race running at 120 (in reality more like 114mm) I hated the way it felt. Now this was a medium, and I ride large, it was set up for a much lighter rider, and I'm a big unit, and I like the Pro twitchy fast steering which makes it both a great flat out XC bike and a joy on singletrack, but the modded version felt a bit less responsive. I might still pull mine apart and give it a go one the summer is over and see if the extra 20mm makes me more 'adventurous'!
But out of interest what other departures from standard spec/mods have others gone with?