Yes, a CIC can change its articles of association. This is done by special resolution, so at least 75% of members must agree to it. The basic procedure for doing this is at the link below, but you'll need to check your current articles, as they sometimes include special rules for how the articles can be amended. Once you've passed the amendments you have to send a copy of the special resolution and the new articles to Companies House within 15 days.
The number of directors you can have depends what it says in your articles, as there is sometimes a minimum or maximum number in there. If the articles don't set a limit, then the minimum is just one. Of course, you can amend the articles to remove this limit. The disadvantage of just having one director is that the CIC's governance will be weaker governance and it will look you are running as a "sole trader" rather than a fully fledged social enterprise, so is less likely you will get grant funding, etc. Most funders insist on a minimum of three directors for this reason.
Hope this helps
I've copied below an example resolution to amend the articles:
[COMPANY NAME] C.I.C.
The following was passed as a [written] special resolution on [DATE]:
The articles of association of the company are amended as follows:
1. For Article [X] substitute [X].
2. Omit Article 
3. At the end of Article [X] insert [X]
An alternative is to pass a special resolution with the following text and the new articles attached to it.
The Articles of Association shall be altered so as to take the form of the Articles of Association attached to this resolution are in substitution for, and to the exclusion of, any Articles of Association of the company previously registered with the Registrar of Companies
I'm happy to have a quick look if you can either upload here as a file or send to me via this Dropbox link.
Thanks James, I've sent them to your drop box (If i've done it right!)...
Article 15.2 sets the quorum for directors' meetings at 2 but article 12 talks about the possibility of the company having a single director. I suggest you tidy up this inconsistency.
Otherwise I don't see any restrictions on changing your articles or on how many directors you can have.
Your objects in article 5 are stated to be "without limitation" so you could probably carry out additional activities without amending your articles, but I agree it's tider to replace it with a broad statement of what you intend the company's objects to be now.
In the schedule 1.10 is supposed to be the name of your company, so I suggest you add this in whilst amending your articles.
Thanks for your reply. Do I just do an amendment for now to tidy up the bits you have highlighted? And then pass a special resolution to make the changes (which we are not doing right at this moment anyway so no rush).
All changes need to be approved by special resolution, you can't just tidy up the wording without going through the formalities. In your case I'd recommend doing all the changes at once using the method I mentioned above (attaching a copy of the new articles to the resolution). This then needs to be sent to Companies House.