It's not that bad, I'm only on the first floor, more of an inconvenience than anything else. But yeah, it makes me long for the day I've got a garage to work in. :)
Just picked up this nice little tool tote thing from B&Q, £10. All my tools live in an upstairs flat so ideal for taking a few bits that I need for a job down to the car.
http://www.diy.com/departments/bq-420-mm-230mm-tool-bag/257272_BQ.prd?Clearance_Tools
Also a selection of spanners, ratchet...