both of these should be done by a good solicitor but I've had some dodge experiences with them so best to cover off yourself too!
Land Reg leave to your solicitor as that's why you are paying them conveyancy. The planning - just pull the file on the property from the relevant Co Co office and have a look at what was done, if anything. Then check the current house map/plan against what is in the file. Any diff. is debatable. If it is there a long time, then retention is a possibility - I would make it subject to the contract you are signing - buy subject to retention being granted or else €x off if you still want it - def. don't go ahead without checking or basing your contract on the outcome
Congrats on your new house