It's a quality frame - no doubt of that. It looks like the original paint was white, since the lower end of the fork steerer tube is white. If there is a lubricating port on the non-drive side of the BB, the frame is likely early 60's, if no oiler port, it looks like late 60's

Have a close look at the fork steerer tube, there should be a serial number on the fork steerer as well as the identical number stamped on the frame; under BB, NDS outside rear dropout or inside of rear dropouts.

All the parts indicate the 1960's.

In the 50's to about 1978, there were only two types of tubing, professional level Columbus, Vitus, Reynolds and seamed straight gauge "gas-pipe". If you can fairly accurately measure (+- 25g) the weight of the frame, you can determine whether it's gas-pipe or pro-level tubing. If below say 2200g its Pro-level and above likely gas-pipe. However, looking down the seat tube or head-tube may reveal a seamed tube.

The thinness (at least apparent thinness in the photos) of the head lugs indicate a "name" maker.

It screams British made to me.