Setting it up as a fixed gear certainly makes the task of acquiring appropriate components much less difficult. I would try to do the minimal amount to this frame if the task were mine. Arresting the rust on the headset cups and perhaps a soak in evaporust or similar. Perhaps gently apply a cleaner to the frame itself. Removing the tape from the seat stays could be a roll of the dice, and I'd be torn between leaving them be (and perhaps not arresting corrosion that may be going on underneath them) and taking them off (and risking exposing an area that might be stripped of paint entirely).
There's a Raleigh restoration group on Facebook, and the majority of the members are in the UK, and some have quite a great deal of experience with the various restoration methods - ranging from wiping with an oily rag and Autosol all the way to a complete respray. I can assure you that they would be quite pleased to hear from you and provide helpful suggestions.
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