Blimey, I know this is the spotters forum but you seem to enjoy a consipiracy theory...
One might suggest that the routing isn't down to any of the above reasons. It's more likely that the crew are simply flying in the airways system and as strange as it may seem, this is the best airways routing in and out of Doncaster for them.
Being from the Ukraine, they probably don't want to leave the airways system or the protection offered by controlled airspace any more than I would if I was over the Ukraine or Russia. As non-native English speakers, their passable standard of English will make it far more comfortable and predicatable for them in terms of the instructions they're likely to receive, the stations/frequencies they'll expect to talk to and the seperation they will receive from the controllers against other traffic.
It is not possible to leave Doncaster and fly immediately to the east without leaving the confines of controlled airspace. At that point they will be in the 'Open FIR' where they will not necessarily be separated from other traffic by controllers, in addition to them being less sure of whom to talk to and what service they might receive. So flying direct to destination is not a practical option for them or most other commercial traffic. Similarly, routing via Otringham is not gainful.
For a better indication, open
www.skyvector.com and find Doncaster. Use the map controls at the top right to choose 'World Lo' and 'World Hi' - these will show you the low-level and high-level airways respectively.
I'd suggest they left Doncaster on the noise preferential departure to UPTON, whereby they joined the Y250 low airway going past Leeds to GASKO, then the P18 airway to NATEB near Newcastle. Thereafter, it looks like P18 to CUTEL and then L983 to PETIL to the boundary of British and Danish airspace.
Hope this helps to illuminate the routing issues and the reasons for what might otherwise seem odd routings.
