I don't have a recommendation for the Limerick area, but if you contact your oil supplier, they may have a list of local installers or be able to give you some advice on it - assuming no one on AAM have any personal recommendations.
If it is used for central heating the best person to ask is the person who services your oil boiler, followed by asking at your local plumbing hardware store,
look for a boiler installer. They can drain it off and reset it in a different spot and also follow upon your pipe work.I'm assuming you have had your oil siphoned off. If so then mention this to the installer as where they secure the pipework will also have a bearing
Its a kind of a job that plumbers don't want to do because it involves a bit of digging out side. its not rhat technical to do yourself but will need to do a bit of digging yourself. Its a job i would do in the summer; wait till tank is near empty and drain tank in to 5 gallon drumbs, move tank to new location put up in blocks tilted back and dig trench to boiler and insert new pipe along trench and connect new pipes , test fittings for any leaks and bleed boiler Job done. 30 quid and One days work i would say but Of course if you want some lad will make a big job out of it and bring in mini digger and charge you about a grand.
OP, hire a builder to dig new trench for foundation for your tank size allowing 300 mm all round. Tank must be at least 650 mm away from any boundary wall. Run the tank down completely and then get plumber to move it and connect in fittings. It is a 2 or 3 man job to move a tank.