Dropping my €0.02 in here - yes, 28/19/13 east with 19 east on the focus on a zone 2 is certainly doable, but it is not without it's compromises. First, you'll need some slim-ish LNBs otherwise you won't be able to get the 13 east LNB to peak for the best signal. Analoguesat recommends using only Sky LNBs for this set up because of the LNB shape required, but in my experience the Sky LNBs are too "fat" and wide to have them sit side by side even on a zone 2. In my set ups for this, I've used either Inverto Eco or Inverto Premium LNBs (both of whom whose LNB caps are 48mm in diameter) for 13 & 19 east along with a relevant adaptor for the LNB holder on 19 east. You'll probably find that the two LNBs will need to be touching each other to get the best signals for both satellites. 13 east will need special attention to get it right as the DVB-S2 transponders (the Polish ones in particular) need to have the LNB placement & skew spot on.
If you get a Sky LNB supplied with the dish, it can be used for 28 east. I'd do it's placement after you have 13 & 19 east done first. Again its alignment requires a little care - the UK spot beam channels mostly come crashing in but the channels on 2A and Eutelsat 28A will need to be peaked as they transmit weaker signals.
For my "homing"(strong signal) & "fine tuning" (weaker signal) of the offset LNBs, for 13 east I try to get RAI 1 to home in on, and then either use Stars TV to fine tune, though if I only have a DVB-S SD receiver on hand I go to RTPi to fine tune instead. For 28 east, I home in first for a Channel 4 SD signal, and then to fine tune I go to FilmOn TV. Hopefully when Astra 2G is in place early next year and 2A plus Eutelsat 28A have been retired from its main duties, signal strengths all round should be good though I have found channels on the European beam of 2E & 2F to still be a few percentage points down on signal quality compared to spot beam signals on the same craft.
Going west of 13 east (with 19 east at the focal point) then starts to get tricky. I'd say unless you are planning to use the Inverto Connect slim LNBs** then 9 east is a no-go. I've managed to get 5 east (Euro beam) with the LNB nearly touching the 13 east LNB but that doesn't have the greatest of rain margin and beyond that you're really pushing the limits - at best you might get Al Jazeera on 1 west but not much else. With the dish fixed at 19 east I've managed to get offsets for CNN Turk at 42 east and France 2/3/5 at 5 west, but these are strong signals at these positions, have little rain margin plus you aren't likely to get much else from these positions. In my experience the gain of the Zone 2 dish starts to more heavily roll off around +/- 10 degrees from the focal point.
If you can try and do so, I'd see if I could get an 80cm dish for such use as you then have less constraints to work with - a Sky Zone 2 dish itself is nearly as wide as most 80cm dishes anyway (the Mk3 dishes are 78cm across) and would give better rain margins across all positions, plus you might also be able to add 23.5 east or even maybe 9 east using the Inverto LNBs I mentioned earlier. However once you start adding on too many LNBs things start to get complicated and compromises may have to be sought. I'd stick with three LNBs for now unless there is something at another position that you really want.
** These LNBs don't seem to have a great reputation in either wet conditions or for fringe conditions. The same seems to go for most narrow-neck LNBs though the Alps LNBs are seemingly OK.
