Have you paid yet? Hopefully not, because i would be suspicious of any hotel that demanded payment in full for a service you have not received.
On the bright side, more than 50% of the reviews are excellent, which does suggest that things are done better more often than worse by a considerable degree.
You need to make it very clear in advance what you expect, and what the consequences will be if you don';t get it.
Arrange an appointment with the manager in charge of your reception. Explain that although they deal with dozens of weddings in a year, you are only going to deal with this one, so your interest in it is conserably higher than his.
Be nice and reasonable, but firm. make sure he understands that barring exceptional and unforseen circumstances, you will not countenance anything spoiling your day, and you are sure he feels the same, and wants to offer you a great day, and enhance his venue's reputation but ...
if you are subject to avoidable problems - sloppy service, bad food, what ever, then you will have to consider your position - but don;t be specific.
If, God forbid, things go wrong on the day - get hold of the manager - you will have ensured that he will be on site on the day, and advise him that if problems are not rectified to your satisfaction immediately you will be witholding 75% of the agreed fee.
You are legally able to do this. You write a formal letter advising that the event was 75% below reasonable expectations, and you are therefore offering 25% of the cocts which is what you feel the event was worth, and the hotel are welcome to sue you for the remainder.
By doing this, you are not refusing to pay - which is illegal, but disputing the value of your service - which is legal.
You should keep this card up your sleeve for issues on the day, and from the averages on Trip Advisor, it should not be necessary. <