All the Harpsichord Makers and Technicians listed below are personal friends of mine and are highly recommended:
Wiltshire and Kent: Cesar Hernandez. Works with Lucy Code, square piano restorations and part time at The Richard Burnett Collection. He has an Italian harpsichord available for hire and is willing to do tuning and maintenance in situ, as well as working from his workshop in Wiltshire. Email cesarhernandez1967@hotmail.com http://www.fortepiano.co.uk 07463325335
Bristol, South West and South Wales: Daniel Flew, tuning, servicing and repair. dan.flew@hotmail.co.uk http://danielflewharpsichords.co.uk 07845187108
Cambridge: David Wright undertakes repairs, servicing and concert hirings. David is also an excellent harpsichordist. +44 7941 093066
Also in Cambridge, Dan Tidhar, tuning and hiring, including Fortepiano: http://www.cambridge-baroque-labs.com
Scotland: Edinburgh, William Hendry, Tunings, Hirings, servicing and repairs: 07929708448
Manchester: Alex Temple, harpsichord tunings and maintenance. 0161 7943717.
Yorkshire: The Early Music Shop, new and second-hand harpsichord sales and spares. http://www.earlymusicshop.com/
Shropshire: Ludlow, Edmund Handy. Clavichord maker, tunings, repairs and restorations of harpsichords and clavichords. http://www.edmundhandy.co.uk
Norfolk: Alan Gotto, new instruments. Website: http://www.dsn.co.uk/agotto/
Oxfordshire: Simon Neil Harpsichord hire, transport, tuning and servicing. https://www.simonneal.org.uk/
London: Andrew Wooderson, Maker, Hirings, tuning, servicing, maintenance courses, second-hand instruments - based in South East London. http://www.woodersonharpsichords.co.uk/
South Coast: Malcolm Rose, Maker, restorer, maker of harpsichord wire, tuning and hiring. Website: http://www.malcolm-rose.com/
Hampshire: Andrew Durand, restorations, repairs and tunings. Sells used instruments. 01428 656246 Website: http://www.musicroomworkshop.co.uk
Somerset: Peter Barnes (that's me!) 07733619002 peterbarnes850@btinternet.com
International: Carey Beebe has a list of European Harpsichord Makers on his site http://www.hpschd.nu/index.html?nav/nav.html&t/welcome.html&http://www.hpschd.nu/l/links-12.html
Carey Beebe's world beating site has so much useful information on tuning, replacing strings, plectra, etc. He is a world leader for harpsichord information. When you have some spare time, please look on http://www.hpschd.nu/
The British Harpsichord Society also runs a useful website which hosts advertisements for used harpsichords and clavichords http://www.harpsichord.org.uk/
The Early Music Shop caries a stock of spares and used instruments: http://www.earlymusicshop.com/home.aspx