If you can't get the offer to appear, try https://www.tmlewin.co.uk/shirts/?src=TIESHI1995SFD30
It is showing 4 for 100. But, Here's how I got the offer: Googled Charles Tyrwhitt Tm lewin showed £19.95 all shirts on the 2nd link. Please see the screen shot. Hope this helps.
I quite like my TM Lewin shirts, but I think if I had to choose I'd go for CT shirts (TM Lewin don't seem to do many shirts with cutaway collars now which is a shame)
Personally, I prefer Charles Tyrwhitt shirts