Wetherspoons are in the wrong to deny you footage.
This is an extract from
CCTV.co.uk which explains most of it.
If you click on the link there is a template to request the footage, however, be aware, publishing the photo (when you have requested the CCTV from them) could be considered a breach of the data protection act by you, and could hinder any prosecution if you ask for help finding the "thief".
How to request CCTV footage in the UK
CCTV Systems in the UK are covered by the Data Protection Act 1998 – and because they are, you can request footage of you from the organisation that operates the CCTV equipment.
For example if your bag was stolen in a pub – you can ask the landlord to make available to you footage of the theft.
There are certain elements to be aware of mind you…
You have to request in writing to the owner of the CCTV system (these can often be found on signs close to the CCTV System)
You will have to provide them with information about the times you wish to view, these must obviously correlate to the times you were filmed. You might want to consider adding in the letter a description of yourself and your clothing.
The organisation must issue you with a copy of the CCTV footage within 40 calendar days.
They may charge you a fee of £10 for this.
Consider including a photo of yourself to help the CCTV operator identify yourself more easily.