Find the stopcock fuse box and meters on day one
Before anything else locate the water stopcock the consumer unit and the gas and electricity meters. Photograph the meter readings on the day you take possession and send them to your supplier. That photograph settles almost every opening bill dispute.
Change the locks
You have no idea how many keys exist for your new front door. Changing the barrels costs very little and is the cheapest peace of mind available to a new owner.
Sort insurance from exchange not completion
Buildings insurance should be in place from the moment you exchange contracts because from that point the risk is usually yours. Check the policy covers the property while it is empty if there is a gap before you move in.
Service the boiler and test the alarms
Book a boiler service in your first month even if the seller claims it was done. Test every smoke and carbon monoxide alarm and replace any that are more than ten years old.
File the paperwork you will need later
Keep the TA6 property information form the EPC any warranties building control certificates and guarantees together in one folder. When you sell the buyer's solicitor will ask for all of it.
In short
Meters locks insurance alarms and paperwork in week one. It takes an afternoon and saves years of hassle.