Relate offers relationship counselling for those having relationship problems: http://www.relate.org.uk/
Marriage Care also offers counselling from a Christian perspective: http://www.marriagecare.org.uk/
Mediation resources are often a local issue but there are some national websites which can be used to find resources.
The Family Mediation Helpline:
http://www.familymediationhelpline.co.uk/
National Family Mediation:
http://www.nfm.org.uk/index.php?page=Home
Family Mediators Association:
http://www.thefma.co.uk/
Family Mediation Council:
http://www.familymediationcouncil.org.uk/
There are a number of websites on collaborative law but the website Collaborative Family Lawyers: http://www.collaborativefamilylawyers.co.uk/ provides a good level of detail. A search on Google will reveal a local collaborative law website (if there is one), e.g. http://www.nottinghamcollaborativelaw.co.uk/