Vintage Peugeot conversion help and tips please

Seatpost is from decathlon, original wasnt quite long enough.
its not exactly the right size, but come with a shim, that if you cut in half fits pretty well.
heres the one
http://www.decathlon.co.uk/EN/l330-basic-diam-23-4-25-27-2-35412401/
pretty cheap and looks nice (IMO)

I'd just like to add, I did go and buy this as it was only a tenner, much appreciated ( I'm sure decathlon has been mentioned as supplying smaller seatposts elswhere too).

The seatpost itself is good and solid, looks much better than what I had (older three piece seat clamp and very short post), however the seatpost is slightly too small, as you mentioned.
The smaller of the two shims was far too thick to get the post fitted into my 80's HLE frame, not sure if seat tube sizes vary within the Peugeot family throughout the years? Anyway, I cut a coke can into a flat sheet, and made a shim from one wrap of that around the post, which fits perfectly.
Hope this helps if anyone else has any trouble.
Cheers

edit: 103 frames should have 23.4mm seatposts, which matches the decathlon with no shim, I assumed HLE 'mangalloy' was the same as 103, so I cant figure out why my seat tube size lies somewhere between that and the 26.4mm of frames like the PX-10, the closest match seems to be the '78> Versailles, which is 23.8mm
So maybe all HLE frames are 23.8mm in which case this seatpost will need a .4mm shim, which it isn't supplied with.