Just looked into this (extensively!!) as I was about to do similar but project is now on hold as we're moving house. In summary:
1. Coolgame - various Landig options but you need the "big red" to get the height to hang a red (particularly a stag). Not cheap but come well rated. Option of importing direct from Landig (see previous SD threads) isn't as cost effective as it used to be. I priced it up and wasn't worth it frankly.
2. SH - buy some used insulated panels off eBay, cut to size, add an old chiller unit and get someone to install piping and gas. Have a look on eBay and probably some companies who would provide a secondhand / refurb'd unit with either a monoblock (single unit won't need any plumbing) or split unit (will need plumbing in and gassing by fridge engineer).
3. New modular - this is the option I'm going down once we get moved. Basically a bunch of ready-made panels that lock together with cam-locks, a door and a monoblock chiller unit (plug and play). You can generally get them any size you like (in about 200mm increments) from about 1160mm x 1360mm (external). Panels are 80mm thick, so this gives you 1000mm x 1200mm internal dimensions, less the bit of the monoblock chiller that hangs inside. Heights also vary from about 2000mm upwards (again, external so less floor and ceiling thickness to get your internal dims). You'll want >2000mm internal height to hang a red.
Some of them come with meat rails as an option, or alternatively these get a good review on another SD thread:
Meat Rails and are cheap.
I got a lot of good advice and quotes from Glacier Coldrooms in the NW, but sure there are some decent companies located more closely to you...
