Zone 2 dish, yes - in principle.
But your intentions are not entirely clear ............
ie If you are using the Sky dish for 28E and intend to carry on doing so, then a Monoblock would only be of value for getting 23.5E with a standard 6 degree device (I know the Satellite separation is less, but it does work). To get 13E or 19E would require a multi-LNB bracket and possible realignment away from 28E (but using an offset LNB to carry on receiving it).
If you are proposing to realign the dish - or have a spare dish - then a 6 degree Monoblock on a Zone 2 dish will work for 13E and 19E.
There have been a couple of Threads in the past few months about using a Zone 2 Sky Dish for offset reception, so have a gander around the archives.
PS: You can get Monoblocks with fixed spacing other than 6 degrees (eg 3, or 4.5 degrees) and you can get one adjustable up to 12 degrees.