You need to maintain or repair your property, but cannot see a way of doing this with going on to your neighbour’s land, perhaps to erect scaffolding, or you may need to work on trees or hedges, or perhaps drains serving your property.
You need to start by looking at your title deeds. Properties built within the last hundred years or so often have the benefit of rights over adjoining land, but the older the property the less likely this is to be. If your property is leasehold the lease should provide the answer.
If you do not have an applicable rights and your neighbour is not willing to cooperate, what can you do? The Access to Neighbouring Land Act 1992 gives the court the power to order the neighbour to allow access. It is rare for anyone to need to rely on this legislation, as the issues are normally resolved amicably, but it is useful to bear in mind what may happen if agreement is not reached. The court would need to be convinced either that the works cannot be carried out without access, or it would be ‘substantially more difficult’ to achieve them without access. The court can award compensation to the neighbour and the right to an order is never absolute, the court will take potential disruption and hardship to the neighbour into account.
It is important to remember that the Act can help if you want to repair or maintain, it cannot be used where your aim is to improve your property.