I did a conversion on an older road frame (126mm) to a Nexus 8 (132mm) and the cold setting of the rear was not difficult. I took my time and slowly spread the rear forks using a piece of threaded rod, washers & nuts. I slowly turned them, measuring frequently with a metric tape measure until the desired spacing was achieved.
I do not know the spacing of the Raleigh DL1 but Shimano makes a 7 speed hub (126mm) and a 4 speed not in production anymore that is 120mm. I think Sturmey Archer makes a new 8 speed hub that can be as narrow as 117(?) depending on the spacer configuration. I would check the Harris Cylery website as they list the spacing for all of the internal hubs they sell. Good Luck!