Review of Site Copy

General update of copy across the site to address inconsistencies, factual errors (eg in outdated text), typographical errors, language and tone.

* [ ] about-branded
* [ ] about-campaigns
* [ ] about-constituency
* [ ] about-contact
* [ ] about-copyright (#122)
* [ ] about-feedback
* [ ] about-guidelines
* [ ] about-linktous
* [ ] about-lords
* [ ] about-qa
* [ ] about-us
* [ ] about-yourrep

* Closes #91.