No you are not able to marry on a visitor visa
http://www.ukba.homeoffice.gov.uk/vi...s/eligibility/
You must also show that, during your visit, you do not intend to:
- take employment, produce goods or provide services, including the selling of goods or services directo to members of the public;
- undertake a course of study;
- marry or form a civil partnership, or give notice of marriage or civil partnership;
- carry out the activities of a business visitor, a sports visitor or an entertainer visitor; or
- receive private medical treatment.
