Hi grinch - welcome to the forums!
Yes, my garage is only a single one, and is built into the house. I can't remember the exact measurements of the top of my head, but I believe it's a 'standard' width, and slightly longer than 'standard' by a couple of feet, due to our staircase running over the garage at that point (you can see that in the photos).
That extra space was used up by my work bench, so it doesn't give me any more room.
I managed the build by only buying what I needed when I needed from Marlin. They do the kits in a number of set modules. As you can see from the blog, I started off with the donor car, stripped it and refurbished the parts before even ordering anything from Marlin.
The I ordered the chassis, and then the other kit pieces as required. I tried to persuade my other half to let me store parts in the spare room, but she was having none of it!
Even with all the body work on now, I still have ample room to get around all sides of the car. Small fabrication or assembly jobs can get done on the work bench, larger ones usually get done outside on the drive when the weather is OK.
The thing I found most of a pain was getting the bits for each module, and then trying to find places to put them until they where put on the car. Lots of shelves help - I put mine up high to clear the main door when it opened, and had them run across the top. Bigger bits tend to live in the seat / foot wells until needed, or until they're in the way and you need to move them. There's a lot of that.
You do also have the option of putting stuff under the car if you use the build stands Marlin can rent you, as it puts the chassis 3ish feet up in the air. Again, good place, until you have to move it to put something on underneath.
I'm sure the other chaps will chime in with handy hints on how to build in confined spaces - Peter did the majority of his build in a single lock up that didn't have any power!
Cheers,
Jason (GOO)