Freehold / Leashold

We bought a property back in 2014  - it was a leasehold property and we purchased the freehold.  We are now looking to sell the property and there is still a leasehold title showing WK281134. How do we get this rectified?

Sarah - it doesn't always need to be rectified as there's nothing 'wrong'. The property is registered with both tenures and in the same names and with a mortgage covering both. As such when you complete on the sale the buyer may, if they wish to buy both tenures/titles and request 'merger' when they register. A merger, if requested, would close the leasehold title and leave just the freehold.
If for some reason you want or wish to close the leasehold title before selling then PG 26 section 3 explains how. Although you'll need to work with your lender and a conveyancer to achieve it - Practice guide 26: leases – determination - GOV.UK
Land registration is complex, designed to protect legal and financial interests in property. There can be significant consequences for any error. Please consider seeking legal representation. Before making an application without legal representation, It is important to consider the benefits of using a conveyancer.

Thanks for the response Adam. Excuse my lack of understanding. Should this merger have taken place when we bought the property. I am confused as to why there is a need for the 2 titles.

Sarah - no apology necessary as this would be something your conveyancer/mortgage lender would have dealt with and explained at the time.
There's no 'should' involved as it's really a matter of choice. Many leases include rights for example that would be lost if you closed/determined the lease and a merger is just one way of doing that
There's a need for two titles because firstly there was a lease granted so that means you can have a freehold and a leasehold. 
If at some point they then come into the same ownership, as has happened here, the lease can be brought to an end as explained. But you have to request it - we can't just assume that's what's wanted and of course if you buy both and we get a transfer and mortgage referring to both we will register it. 
The fact that you bought and own both tenures/titles has zero impact on you hence I suspect no awareness for the past 11 years since you bought. And still zero impact unless your buyer for some reason insists on you merging them both before they complete - your conveyancer can hopefully explain it far better than I from their perspective though