Thank you all so much for your input. It really is just so useful and reassuring to know what is normal and what to look out for (I've read the books and loads of posts here before, but... when it actually happens inevitably the questions that comes up is a slightly different one).
Been out on the field again for quite a while, just watching, and I'm think I'm satisfied now that all is indeed OK for the wee chap. I saw him suckling twice and she holds still for him, and they bleat softly to each other when she grazes a bit too far for his liking. He was walking around exploring for a bit, he seems really curious and alert, he then settled down again for a snooze, so I went up to him and quickly felt his ears and mouth (warm) and sprayed his navel. Will stop myself from going out there again until the evening now. The rest of the flock including the ram are keeping a respectful distance.
The weather is showery here not really raining in sheets as it did yesterday - the field has a lot of natural shelter (hedging and overhanging trees) but she seems to have chosen her spot more for being a good vantage point than a sheltered position. I think it would disturb her to build a unfamiliar shelter structure around or very near her - so I'll just leave her to be for now.
(I do have a field shelter, but this is used by the donkeys overnight (they are out on the other field during the day) and the sheep don't really spend time there, so unless in an emergency I would not want to put her in there as she'll get stressed out by the unfamiliar space.
Piccies to follow!