First off, I'm American, so I don't know prices in pounds or Euros, only USD, and I had to verify what A0 and A1 sizes were in inches, so bear that in mind with this response.
Yes, there are both color laser and color inkjet printers that can handle A0 and smaller sizes. While the prices for a large format color laser printer is $20K+, its cost per print is fairly low, however it only becomes cost effective when printing in fairly large volume. Most map printing shops can't justify a color laser printer. Inkjet printer/plotters while much less expensive for a unit, has a higher ink cost than laser, however it is still fairly reasonable to print - especially in the lower volumes found in the map printing business.
As mentioned on another thread, I use a Canon IP 8100 44" wide large format inkjet printer in my Gamer Printshop. Though I've used HP, EnCAD, Kodak inkjet printers - for best value I've found this printer is a tremendous value. Basically the unit costs around $6,000 USD to purchase (compared to most HP printer/plotters which cost around $15,000+)
Many large format color inkjet printers require a RIP (raster image processor) which can be a dedicated hardware RIP server (standalone PC built to manage and process printing) or a software RIP like PosterShop. A hardware RIP with necessary software might run you $4,000+ while a software RIP costs $1,500+. Some printers like the Canon IP 8100 can work with a RIP, but can also print straight from Photoshop, making it more cost-effective than those requiring RIPs. However those digital printing houses that print multiple prints, in multiple sizes, of multiple files for different clients are better off using a RIP, as the prints are nested to waste the least amount of paper printing multiple files from the queue.
For color scanners you're basically limited to the roll traction feed type scanner, which limits scanning to loose paper sheets with color maps prints on it. If the map is on thick media or is fragile because of age or condition - this type of scanner will not work. As the traction feed pulls the paper across the camera exposure lens and could damage or otherwise not fit in the media feeding "mouth". A color roll type scanner will cost around $10,000+
Of course a primary graphics dedicated PC is required to run the whole production, whether that's a PC or a Mac, depending on the system you use.
So basic hardware needs: large format inkjet printer, large format roll-feed color scanner, a dedicated PC, and possible a RIP (hardware or software).
Other hardware additions to consider:
1. A large format flatbed scanner (in sizes 11 x 17 up to 18 x 24; $1,000 to $5,000) - I have a 12" x 18" flatbed
2. For the truly color "anal" client (there are a few) a colorimeter or similar device is used to check colors in an original, so it matches in the digital scan and the final output print, though none are cheap ($2,500+) - though I don't use one.
3. Large format laminator - to seal printed maps for better duration in handling, outdoor use, or for use on a tabletop RPG game, you'll need one that matches the inkjet printers print width - though a 48" or 62" wide laminator will run you about $6,000 - I have a 38" laminator in-house. A hot roll laminator is preferred to hot-shoe type laminators or cold press laminators, though the latter are less expensive.
Although any shop can use more toys than that - those above are the basics and basic add-ons for the scenario you describe.
I hope that helps!