Location of Ordnance Survey Numbers

Within a Title, under C:Charges Resister provided by HM Land Registry, it notes the following:

'Ordnance Survey Numbers 15 or 17' 

Where am I to find these maps?

These are noted multiple time with no specific grid reference or location and are not contained within the searches.

Emlyn - which title number please?

Adam - Title Number: WS42775

Emlyn - many thanks. So the Note against the entry C3 explains how the land in the title comprises part of Ordnance Survey number 15.
If you are looking for a map that confirms where OS Numbers 15 and 17 are then you would need to contact OS to apply for/view historical OS map data from 1977 or around that time.

Adam - Many thanks. This is something which 'you' do not hold on file?

If this is unable to be found please could you advice on what this means to the interpretation of the Title?

Emlyn - we don't hold the information on file. The 1977 deed would not have been retained at the time of registration in 1990.
It's not needed as the Note explains how the land formed part of OS Number 15 so the 'interpretation' is that the land in the title is bound by the restrictive covenant as set out in the clause (b) in entry C3. You don't need to know where OS Numbers 15 and 17 are as a result