Both groups and individual constituents can visit Parliament. My office can arrange tours of Parliament and Big Ben as well as gallery tickets.
Parliamentary tour guides take groups of up to 20 around the Palace of Westminster free of charge at these times:
Monday & Tuesday - 0900-1200
Wednesday - 0900-0920 / 0925-1200 (Lords only)
Thursday - No tours
Sitting Fridays - 1530-1700
Non-sitting Fridays - 0930-1700
Information on Big Ben Tours can be found here: ttp://www.parliament.uk/about/visiting/big_ben.cfm | 
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