Hi, Our landlord has just got planning permission for a new house to be built in our garden. We were told orginially that this was to be a long term investment and that we would be able to renew. Assuming that we can stay a bit longer does the right to enjoy peaceful use of the tenancy stretch to the garden so can I refuse to let anyone enter the garden (and thus view the plot) unless I get a rent reduction etc. Grateful for info. Thanks

All depends on what is in your tenancy agreement. If the LL retained all rights of access to a bit of the property (for example, if there is a shed / garage at the bottom of the garden where he keeps various tools etc) possibly not. If the agreement refers to the garden as part of the letting, he hasn't a leg to stand on.
He may just have got planning permission in order to increase the value of the property when he comes to sell - he's got several years before it expires.

Did you look at the plans? They should be available for you to view still on the council's website. If you've not already then I'd look now.

It's probably only the same as next door building so you might not be disturbed too much - but it can affect your water supply, telephone if cranes get in the way, noise early in the morning, lack of parking spaces.
In the long term if your garden space is reduced and parking made worse you will have to discuss a rent decrease.
Or more.
Or threaten to. If he's going to build he would probably rather have a pair of eyes acting as security on his building site and might reduce your rent if you stay.

It all depends on whether you have any right to use the garden, and if so, what rights.

Chances are that if your property is a house and the tenancy is silent on the issue of the garden, or any reservations, the landlord has demised (ie: let) all parts of the property to you. As such, you would be in exclusive possession of the garden and have the right to treat anyone, including the landlord as a trespasser.

If the property is a flat with a shared or communal garden, then the situation is less clear cut because if your landlord is a freeholder of the building, then he might have retained rights over the garden.

In either case, if he begins to build on the land over which you have rights (whether exclusive possession or merely a right to use the garden), then you might be able to obtain an injunction prohibiting any building until you have given up possession. However, injunctions are discretionary remedies and if you only have a short time left to run on an AST, the Court may well take the view that damages for your loss of enjoyment are sufficient. Damages would probably be quite modest as IIRC, in such circumstances damages are assessed at the price someone would be willing to sell their rights for, not at the "ransom" value of the rights.