Symtomless, I think you're right.
I grew up in Scotland and I live in France and I think Corbyn is slightly left of center. In France, neither Corbyn nor McDonnell would be considered far left. AT ALL. In France they have an actual Communist Party which people vote for quite happily and who are considered properly left wing but not scary Stalinists.
Which, IMO, goes to show a few things:
- the British population is on the whole pretty right wing and many people who describe themselves as left wing aren't at all in European terms.
- The British press is biased, irresponsible and very right wing.
- The Overton window of British politics is decidedly right wing.
If a Labour government had done one tenth of what the Tories have done they would have been SLAUGHTERED in the press and ridiculed out of power for evermore by the public. Just look at what they have done! They inflicted their internal party dispute on the general public in the form of a referendum, they lied in the campaign for that referendum, they made promises they cannot deliver, they have failed to deliver on the result of that referendum let alone delivering what they promised leaving the EU would achieve, they can't keep a leader in place, they disrespect parliament and democracy, they purge their party of moderates, etc, etc.
And that is without even touching on austerity and their unpleasant policies and values.
And people are complaining about Corbyn. 
It's taken me ages to understand what is going on in British politics but when I read threads like these (of which there are many on MN) it just makes me think that it is actually very simple. England is basically a very right wing country and much of its population is very very receptive to a propagandist press telling them that people like Corbyn and McDonnell are akin to Stalinists because they want to renationalize the railways and make very rich people pay a highish rate of tax.
Which I guess is why the UK is in the mess it is. It's a shame though.