Id stick to sportive machines to give you as close as a riding experience to your summer bike as possible, while still accommodating wider tyres, greater clearances, mugguard mounts etc. The usual suspects, Pinnacle Dolomite range,
Ribble (of which im not such a fan personally), Kinesis racelight (Kinesis used to make the frames for the Dolomite, so theyre quite similar in character).
You could find find something similar in steel, although id suggest your roads are just as bumpy in january as they are in august when youre on your summer bike, so the benefits in ride comfort may not be what youre after.
You could go for a light tourer, but you start to deviate from the nature and character of the summer bike. Itll likely do a stellar job, but it brings a totally different riding experience.
Id personally steer clear of adventure bikes in their various names and forms. They do pretty much everything, but are good at nothing. Theres no compelling argument in their favour aside from folk only able to own one bike for some reason and wanting to ride it everywhere.
One important note - whichever way you go, you cant make an informed decision from a brochure. The shiniest bling groupset (more accurate, geartrain - virtually no bike anywhere is supplied with a genuine full groupset so don't get sucked in by the guff) wont make a leaden, uninspiring frame feel joyful, reaponsive and lively, whereas a cheap groupset on an excellent frame will still deliver a decent riding bike. Also, be wary of geometry comparisons - somethong as simple as tyre section can affect the trail measurement on frames with otherwise identical dimensions and angles and profoundly affect stability and steering, so dont get too hung up on that in the catalogue. Finally, there is no universal method for measuring a bikes weight - some quoute full bikes ready to ride, some without pedals, and some even without tyres, and some don't quote at all, and of those that do quote none of their sizing siystems are 100% directly comparable, so that is hot air as well. It may be tricky at the moment with stock levels as they are in some places, but try and get a test ride - that is the only reliable way of knowing if a bike is going to ignite your Y fronts with excitement, or if it will be merely adequate. 1500 sheets is a lot to drop on the merely mundane when the same cash could get you a real corker.
Whatever happens, best of luck.