You pay your rent on current property until your agreement runs out in July.
Move into your new property whenever you want but remember to write cancelling your current agreement when it finishes in July.
Tell your landlord (best to put it in writing) as soon as possible when you want to leave to give him time to get another tenant for when you leave. No good leaving it until you're ready to go. If he doesn't manage to get another tenant in time you will definitely have to pay until the end of your current agreement but if he does get somebody then he MIGHT let you off the last month, but he doesn't have to.
All correct answers. You are locked in financially until July. You can leave before but you will need to pay until the fixed period is up. You need to give one months notice to your Landlord (or letting agent if managing the property) in writing. The Landlord may let you leave early if they can find someone else to rent the property before your tenancy agreement is up, so that there is no empty period. Your landlord is most likely to agree to this if you let him/her know that you will be very accommodating in showing around/allowing access for viewngs.
if you have been there more than a year, and the place is in good order and immediately re-lettable, why not give 3 months notice and ask for an early release?
i think there is more chance of being released from the final month if they have been there longer, based on my experience of short and longer tenancies and landlords! plus if they give lots of notice - which is the bones of my advice - they are most likely not to lose the month!
You need to read the terms of the agreement. When I rented out a house we had a rolling year on year contract. That didn`t mean the tennant had to stay until the end of the year though. They could give me 1 month`s notice of their intention to quit and I had to give them 3 month`s notice if I wanted them to quit. If you haven`t got a copy of the contract, ask to have one from the landlord/agency.