Freesat uses a Huffman encoding for EGP data, which has not made its way into VDR core.
a) Plugin EEPG has these tables (and covers some other EPGs as well) b) A Freesat patch extends VDR to just the Freesat code tables.
The patch also covers Freeview HD (which uses the same encoding as Freesat, but with standard PIDs instead of Freesat's custom ones), which EEPG doesn't, unless it's been updated since I last used it.
The author of the EEPG plugin has always been very helpful. You should just contact him about adding Freeview HD support. Then you won't have to monkey around with patches and messing with the VDR core.