It can certainly be done, and it can even save some money along the way, but it's a veeerryy high risk strategy and has backfired on a lot of people over the years ... you really want to be 110% up to speed on your basic handling, instrument scan, rules of the air, situational awareness etc etc etc BEFORE you start the IR because you can spend some big bucks real quick in that thing.
Remember that every hour in the twin = 3 or 4 hours in the single, so you have to make EVERY SECOND count towards the valuable business of learning IFR when that meter is running. You don't want to be spending £300+ an hour getting your basic handling skills up to speed in the Seneca before your instructor can get down to the serious business.