The Working for an MP website receives a large number of requests from citizens of other countries for advice on who can work for an MP (or other organisations around Westminster). We are not in a position to answer such enquires individually, but here is some very general information.
All foreign nationals should check that they are eligible to work in the UK before applying for any positions. Foreign nationals must have an immigration status which gives them the right to work in the UK before taking up a post. You can see further information here: FS39-Employing-Foreign-Nationals
The rules for living and working in the UK are different for persons from the European Economic Area and Switzerland than for persons from other countries.
UK Visas and Immigration considers applications for permission to enter or stay in the UK. General visa information for persons overseas and guidance on which visa to apply for can be found on the UK Visa and Immigration website: https://www.gov.uk/browse/visas-immigration
Further detailed information about different types of immigration status and the conditions attached can be found on the UK Visa and Immigration website: https://www.gov.uk/government/organisations/uk-visas-and-immigration