Common refusal reasons for UK Visitors.
(a) Inadequate or inconsistent information
(b) Failing to persuade the Home Office that they are genuine visitors will leave the UK at the end of their visit.
(c) Failure to justify (back with evidence) reasons for Visit.
(d) Lack of family links with own country, for example spouse, children, parents or relatives.
(e) Failing to satisfy they are not coming to work in the UK
(f) Inadequate, Personal financial circumstances such as applicant levels of income
(g) Lack of documentation/ justification to satisfy their contention.
A detailed letter from a representative explaining any issues of likely concern may help gaining visitor visa. Immigration staff guidance about the different visitor categories for visiting the UK and how UK Visas and Immigration makes decisions on visitor cases, Visit guidance