Changing 3 titles into one

I am purchasing a property that is a house that consists of a groundfloor flat and a first floor flat. There are 3 titles, the freehold and two leases (one for each flat), we would be buying all 3 titles. We intend to live in the property as one house but it is appears very expensive to find buildings insurance for a property with 3 titles (and two postal addresses, one for each flat) - it seems that i need specialist insurers and they appear to be charging more than double what it would usually be without the complication of the 3 titles. 
How would I change the 3 titles into one, and effectively get rid of the leases?
 

Freda - if you want to 'get rid' of the two leases then you would need to request that they are 'determined' and merged into the superior freehold title. In order to do that they need to all be in the same ownership, held in the same capacity and all have the same class of title, for example Absolute.
Your conveyancer will be able to advise you as appropriate and one of the key things to check is that the leases don't include anything such as rights that would be lost if the leases were got rid of.
The postal address issue would be something to contact the local authority over to change as appropriate. Once changed, and if the freehold address needed updating, the council's confirmation can be submitted to update the freehold register also

Hi Adam, thanks so much for your reply that's really helpful. Regarding the leases what kind of "rights" might that refer to please?

Freda - that can and will vary but thinking more along the lines of rights over adjoining/neighbouring properties.
The devil will be in the detail re the contents of each lease - your conveyancer would normally check this al for you before recommending merger and closure of the two leases for example.

OK thats helpful thanks :)