The only Raleighs that are 26tpi are the ones that shared the production line with the Raleigh Sports and low-end other bikes at Nottingham or at Gazelle of Holland. This means the non-Carlton models like Record and Grand prix are 26tpi. Bikes from the Super Course on upwards - in most cases - have standard British Threads.
Here are two more solutions :
1. Buy 26 tpi spacer rings from Phil Wood, and then buy any cartridge bottom bracket which allows you to remove the threaded cups from both sides, Shimano UN-72 being the most obvious candidate, but modern campy chorus is another possibility, etc.
2. Buy a square-taper spindle and continue to use the Raleigh / Stronglight / Nervar / whatever cups. This was my solution when I installed a Sugino Maxy on my Raleigh Gran Prix in the mid 1970's.
- Don Gillies
San Diego, CA