Hello!
first you must look what scew angel,
you must set,your lnb
of 28,5 for your location,on this website .you can do this
_www.satlex.de
type in your coordinates east and west degrees,select the satelite ,and after calculation,you see a graphical diagram,of your lnb scew position!
for fine adjusting the sceq,you need a polarizer,with 3 conection cables!
but,i dont know exactly the dishsize is necersary,in your ara for bbc!
a polarizer,takes a proximently 0.5 db,maybe to much,when the signal is very very weak!
,so i dont think you need one,fine adjusting manually,maybe the better way!
invavom lnbs,was often tested,in out of footprint areas !
but,in the meantime,you get better lnbs for weak signals,
i got i report,from east germany,that it was not posible to reveive bbc with a channel master 1,80 m,and invavom lnb,changed to inverto,and the picture ,was here,with the exactly same antenna!
it sounds crazy,but,when i see the signal,difrents,now on my gregory,since i changed from invacom,to inverto,i can belive it!
the last option you have,you buy lnbs ,that are optimeized,for 10-11 ghz range,also avalible for 12 ghz optimeized!
this lnbs,are not avalible here in europe,check
Ebay
usa ,some dealer have it in stock for a couple of $
the problem,you have ,a limited freqency range,but optimeized for it!
greetings from your nabour country!
good luck!!