MPs can assist their constituents from making private enquiries and also raise any topic in the House of Commons.
Initial steps
When a constituent approaches a MP, the concerned MP might privately write regarding the issue to the relevant department or official, might issue a letter to the appropriate Minister or even make a personal appointment to discuss the issue. These proceedings might however at time be time consuming but they give relief to the constituent.
Making the issue open to the public
If a matter is of great importance, then the Mp might publicly announce the same in the House of Commons, where it will be officially recorded and would be brought to the attention of the press and public at large. If these processes fail, a constituent can always organize a petition in favour of the House of Commons or can always lobby the concerned MP.
Personal Requests
A constituent can always request a MP to give a speech at any event, pledge their support to a campaign or write to the local media for the constituent and it is completely the decision of the concerned MP whether he shall indulge in the same or not outside his Parliament duties.