Thanks Bronte. As per post #1, I emailed and also wrote to Revenue, with evidence of the price of the house next door to me that was sold for €85,000, plus values of other similar properties to my own in the area (Dundalk). These were from daft.ie, plus various local estate agent websites.
I then rang them 2 or 3 weeks later to confirm receipt of this info. Was planning to ring the LPT helpline as I had nothing back from them, then the cheque came through the letterbox this morning. Was a letter with a cheque attached.
It didn't specifically state that my band was changed on it, so I logged into my online LPT account and saw my valuation was now €90 for 2014 instead of €225 previously.