Council Tax - a tax on residential properties. Properties fall into one of eight bands, A to H, where A is the least expensive and H is the most expensive. Your council tax bill is made up of the council tax itself which is the largest portion (goes to the council to pay for schools, libraries, street lights, etc). The remaining portion pays for water and sewerage.
Non Domestic Rates - businesses pay these. Water and sewerage are payable in addition. I don't know the ins and outs of how they're calculated.
Unfortunately land hoarding is an unresolved issue in the UK, there isn't as far as I know any penalty or charge - much of this land has no services or business activity so can't be taxed. There have been suggestions by some UK members of parliament that house builders should be forced into a "use it or lose it", thus far there's not been any official position from the government. I suspect the issue will be swept under the table until the next time the media hoves round and puts this back in the spotlight again.
Usually you deal with bad 'land hoarding' with a high enough property tax rate. And if you want to avoid effecting the old and the middle class, you add exemptions for primary residences.