Matching up a new spindle and cranks using a cottered set is going to have many fewer things that have to fall in place. Just finding any ST spindle that fits with the correct Q factor and bearing spacing to match his bike may be a bit difficult in the wide Raleigh BB. Finding 5-series ST spindles is not hard. 7-series are a PITA. Getting a 7-series that has the proper Q and then getting a crankset that puts the chainwheel in the correct place is going to be more difficult.