The Leasehold Advisory Service provides free advice on the law affecting residential long leasehold property and Commonhold
If you have just bought, or are thinking of buying, a flat or leasehold house and are unsure of the rights and responsibilities of being a leaseholder then you should first read their publication "Living in Leasehold Flats". It provides a good, basic guide to leasehold law
www.lease-advice.org.uk/livingframe.htm