Yep SIDs came later- don't know when but maybe Vintage ATCO or Compton 3B (who has named himself after one of them) does.
Clearances mentioned way points (VORs, NDBs or fan markers?) as I have mentioned. The standard south westerly one I didn't mention was Beacon Hill Burnham Chertsey and Dunsfold.
North bounds were at one time join control airspace x miles east of or on track Woburn IIRC. There weren't many so I don't remember clearly- Autair Herald in the evening was the memorable one.
But the restriction at Bovingdon might have come later- may have been easterly Beacon Hill (or Henton it is all such blur!) before that.