Which type of floor for Garage Conversion

Hi
I'm going to do a garage conversion in the near future and would like to use a suspended wooden floor over the original concrete garage floor which is not been DPC membraned. The span of joists from wall to wall is 3010mm but the house floor is only 240mm above the garage floor. The garage floor is one brick below DPC and the concrete is only around 3" thick over packed dolomite so I don't know if I can use sleeper walls without digging up the concrete and putting in deeper founds. Is there any easy way to do this or have I to resort to putting in a new concrete floor up to the level of the house floor?
Cheers for any info given.

a bit unclear what youre doing but....
if you are purely wanting a floating floor over the garage slab then....
get 18mm or 22 mm chipboard.subtract that measurement from the floor difference and fill under with kingspan or similar to even the floor levels.if theres a fall on the garage slad,level off first with sand.after laying the sand,insulation,lay down a 1200 gauge polythene membrane(odd if no membrane under the concrete),than glue your boards together,leaving an expansion gap around the perimeter.the skirting will cover the gap

I did'nt think of that. Would that be OK building regs wise? It seems a lot easier thn raising the present concrete floor to match the house. (I aim to knock thru into the kitchen to make a kitchen diner).
Cheers