That is indeed a 201k and could be 1930s, 40s or early 50s. Not much info on its condition, but I'd say it looks pretty scruffy for £120. It's worth biding your time till the right one at the right price comes along. Another one to consider is the 99k, which is a 3/4 size machine, so more manageable weight wise. That 201 is a beast to lift! The later, more angular 201k was made from the mid 50s and has an aluminium body. Still heavy, but not back breakingly.
If you can find one that has been PAT tested and preferably rewired, that would be worth paying a bit more for, but if it's all original, I'd definitely get it checked out and get a new clam style foot control to use with it. You know you're not in for any nasty shocks then!
Good luck with your hunt, and keep us posted.
Suzie