LPT - want to revise down the valuation of my property

I valued my 2 bed apartment in the €100k - €150k band in 2013. A similar unit beside me sold for €90k last week. The truth is that the property has not been worth over €100k since the property tax came in...I'm in Drogheda. I have been overpaying LPT. I'm told I need a EA valuation letter or solicitors letter to revise downwards the valuation. Is there no other way that won't cost me money...like sending daft.ie links that would back up my case?

Thanks.

LPT is based on the value in 2013. The value in 2015 is irrelevant. In theory we'll all be asked to submit a new valuation next year but with an election due who knows, it may be deferred.