I do congratulate the local authority in the provision of a permissive bridleway which serves a useful purpose but it is not a replacement for the right of way in question.
Just to clarify a few things:
Knowing that the footpath was "hot" I was deliberate in not riding my bike. It was not my intention to antagonise the landowner by exceeding what I understood were my rights.
At the point I was challenged I was certain that I was within my rights to push my bike so I pressed them as forcefully as I could, shouldering my bike and attempting to get past the landowner.
At that point he pushed me in the chest and it was then clear that he was prepared to apply physical force in preventing me from progressing. As the landowner had told me that an off-duty police officer was exercising their horse nearby I then called "police" loudly and a woman approached who denied she was a police officer. I would have telephoned 999 had I been able to identify my location by name at that point.
A shouting match ensued. It was clear he wasn't going to budge and we departed on unpleasant terms; "tosser" said I, "arsehole" said he and made remarks about my bravery in retreat. I returned towards him briefly, remarking on his comparitively large stature and on how that reflected on his bravery.
A couple of hours later, once I'd cooled down, I returned to the site to investigate the situation more closely, perhaps to speak to him again (from the safety of the bridleway) more calmly and to demonstrate that I was not to be intimidated.
It was then I noticed that the signs also prohibited pushing and carrying and I was then unsure as to whether I was in the wrong and actually considered how I might make an apology to the landowner.
When I got home I posted this topic.
As demonstrted by the differences in interpretation arising from max headset and zulu eleven, it is clearly not straightforward!
Thanks all, however, for your comments of support and information.
There's no doubt that there is the experience and knowledge out there, but unfortunately most individual PROW officers have a fairly narrow remit and band of experience - more often than not individual counties departments repeat the same narrow cut and paste interpretation of the law from past PINS circulars as their "definitive" statement of what the law is. 
