http://www.ind.homeoffice.gov.uk/ind/en/home/laws___policy/immigration_rules/part_2.html The requirements to be met by a person seeking leave to enter the United Kingdom as a visitor are that he:
(i) is genuinely seeking entry as a visitor for a limited period as stated by him, not exceeding 6 months; and
(ii) intends to leave the United Kingdom at the end of the period of the visit as stated by him; and
(iii) does not intend to take employment in the United Kingdom; and
(iv) does not intend to produce goods or provide services within the United Kingdom, including the selling of goods or services direct to members of the public; and
(v) does not intend to study at a maintained school; and
(vi) will maintain and accommodate himself and any dependants adequately out of resources available to him without recourse to public funds or taking employment; or will, with any dependants, be maintained and accommodated adequately by relatives or friends; and
(vii) can meet the cost of the return or onward journey.
If you're going to come here as a visitor, you CANNOT seek work or be legally employed.