Insulating floor of existing garage conversion

The Soup Thief

Hi,
Wondering if anyone can give me some advice on a job I'm planning to do. Our garage was converted into a bedroom by a previous owner of the house. There is virtually no insulation so the room gets horribly cold in the winter - must have been a terrible place to sleep! Last winter it was like a heat sink, leeching warmth from the hallway and other rooms. The room (supposed to be a play room / guest room) was unusable November to March.
I'm dry-lining it, improving the glazing and the attic insulation, which should help.
I'm wondering about the floor though. It's a wooden floor, suspended about 4cm above a concrete slab. The floor was cold to the touch last winter. Dry lining will tackle the drafts a bit I hope by improving the seal at the edges / corners of the floor.

But (here's my question) is it worth me trying to insulate the space between the concrete slab and the wooden floor?

If so, what do you reckon is the best way to go about it? I'm reluctant to pull up and replace the floor as what's down is fairly reasonable.
It's a small enough volume under the floor so I doubt if a pumped insulation company would be interested - I've read threads elsewhere online where people have themselves blown polystyrene beads (using hairdryers or Hoovers taped to plastic bags of beads, with pipes as delivery nozels - if I take off the skirting I'd have access to do this). I checked with an inspection snake that I've access to the spaces between the joists and it all looks accessible.
Is this a daft idea?
Has anyone done anything like this?
Can anyone suggest anyone supplying insulation beads near Naas (the silver ones I guess, but I'd think the white ones would probably be better than nothing)?
Is it likely I'd get much benefit? As I say, there's only 4-5 cm depth.
Or can anyone recommend a professional who might be interested in such a small job (Naas)

Thanks in advance for any suggestions

looksee

Not sure how you will do it OP, but I suggest you definitely do it. We had a converted garage like that and it was colder than a fridge. Not only was it unusable but the bedroom above was cold too. We put in underfloor insulation, pumped the walls and insulated the ceiling. It is now a useful room that does not need any more heat than the rest of the house.

The Soup Thief

Thanks, my thoughts too.
I rang an insulation company yesterday- the guy said there's no way of doing it, that pumped insulation is not the right answer for this situation. Thought my suggestion wouldn't work, which is a bit of a bummer. Might ring around a few others