Hi Steve,
This is a common problem with puntos.  I too have a 55 1997 and my back
motor went not so long back.  The motor often goes in these and the
only option is to replace it.  New, you can buy from
www.shop4parts.co.uk  or second hand you can buy from
www.puntosports.co.uk as i did for half the cost at ?25.00 :)

To remove it you need to unscew all the screws from the plastic cover
on the inside of your boot and pull it off.  Its held on with red
clips, be very carefull not to break these!
You should now see the motor and the wiper attachements.  Pretty easy,
just remove the one one and replace the new.  Note the wiper will fall
off when you unscew it, so be ready to catch.  Its a bit of a bugger to
line back up, and mine still isnt as level as it should be, but it
works :)

Hope that helps.

Karla