A crowd called BMD will do it
021-4310743
About 100e callout plus extra then if any pipe work is involved. Not cheap but as you have probably found out, not a lot of people available to do it.
Word of advice: If you are putting an oven underneath, make sure that you make the fitter aware of this and check the measurements to the oven verus where the back wall is so that you know where the pipes need to be and how flush to the wall they need to be. Best of all, be there yourself when they are connecting it up (speaking from experience!!). Also be aware that to connect the gas hob fully there needs to be a power point available to connect up the electric spark capability. Dont think they will connect this off the main oven wiring for safety reasons. I was lucky as I had the plug socket for dishwasher nearby.