Yes you can more than likely fit it, kits are under �50
however its quite time consuming - i think paying someone to do it for you would be out of the question
it involves fitting solenoids in the doors(little pull/push devices) - so involves removing door trim. Most cars without C/L have no wires going into the doors so you may need to drill holes to connect the doors to the car and use some sort of rubber cable protector
then wire it all up
However it will work on a remote control - not by opening the drivers door - i think most kits will be like that
Heres a kit from Maplin for �21.99
http://www.maplin.co.uk/Module.aspx?ModuleNo=1 2303&criteria=central%20locking&doy=22m1