Well that is interesting, having just spent a week in deepest darkest Cornwall in the camper in a field that was at the end of several miles of single track road, I was recalling the question about who has right of way (and I use the term loosely) up a hill, as on one occasion I was about 1/3 of the way up the hill when a car came down the hill (faster than I can manage in the camper) and refused to reverse back up the hill. I was sure that vehicles going up the hill had priority - something to do with it being easier to control a vehicle in reverse up a hill than down if I recall - so I spent a couple of minutes begrudgingly nursing my 40 year old VW down a narrow hill... not that I minded too much as I was also in holiday mode.
Highway code rule 155 has this to say:
155
Single-track roads. These are only wide enough for one vehicle. They may have special passing places. If you see a vehicle coming towards you, or the driver behind wants to overtake, pull into a passing place on your left, or wait opposite a passing place on your right. Give way to vehicles coming uphill whenever you can. If necessary, reverse until you reach a passing place to let the other vehicle pass. Slow down when passing pedestrians, cyclists and horse riders.
So for me to assert that the cyclist has right of way (I should stop using that and say 'has priority' instead) was no more correct than the assertion that driving up hill gives
you priority. He should have pulled in if possible and you should slow down to over take which would have been incompatible goals when trying to overtake a cyclist doing 25/30mph, but there was no MUST pull in, no MUST give way up hill, in the code, so these are the things we
should do where applicable/safe etc.
I will certainly bear this in mind if I am ever cycling on a narrow country lane at speed! I wouldn't hesitate to pull in when going slowly, but at speed, probably not. On the other hand I think if I pulled in in the camper expecting someone behind me to over take, they would probably pull up behind me and start beeping their horn wondering what I am doing!
The way the highway code is written it's all very chummy and feels all 'why can't we just get along'. Probably a product of when it was written. When motorists were proper chaps with driving gloves and goggles and cars were a lot slower to accelerate and stop (like my camper).
I think in answer to your question, no, your weren't being unreasonable, but then I don't think, from my understanding of the situation, that the cyclist was being unreasonable either. Unless of course you are talking about the desire to wear Lycra - that is unreasonable.