Can my sister attend court with me?

My ex has conducted a war of attrition with me due to having enormous fincancial backing..so I'm having to give up my legal rep and become litigant in person.

Can I take my sister into court with me for support, advice etc etc...she's razor sharp and I know would be of great value but is it allowed?

Yes, she can attend as a McKenzie friend. She Isn't allowed to address the court but can take notes and advise you. See this article in the wikivorce library.

The official President's Guidance (i.e. the President of the Family Division) is here: www.judiciary.gov.uk/docs/pfd_guidance_m...friends_oct_2008.pdf

It does say that the MF must confirm they have no interest in the case, though the courts often seem relaxed about this and there are cases where a partner or spouse has acted as MF. You do need to apply to the court as soon as you can telling them who the MF will be (see the guidance) so they can approve your choice. If she wants to address the court she can apply for right of audience which will be granted in certain exceptional circumstances.