In reply to LakeDistrictMountaineer:
I agree that Chromebooks are an option, I've had one for years and think it's great but if one of your main reasons for using it is writing logbooks then you mind find it slightly irritating using Google Docs for everything as sometimes the formatting messes up when you convert it to word - I don't know if you can print directly from a Chromebook either.
I recently got my girlfriends sister a new Acer Chromebook from the Argos eBay outlet store for around 250 quid or something like that, I didn't even realise it didn't have a DVD drive in it at all!! But then afterwards realised that the equivalent one with a DVD drive had a worse processor or something - I personally would go for one with no dvd drive if you're on a budget. It's lighter, less to break and the money is spent on things which make it work faster (e.g. processor and memory.)
With regards to photo storage I'm pretty sure that the most modest modern laptop could store a life time of photos, not to mention free Google Drive space and others for cloud storage etc.
I would go with Windows simply to make it straight forward to use with 90% of other hardware, software and accessories out there. Even though other operating systems may have their advantages.