As
@johnnyb47 has said above, Aldi and Lidl often have inexpensive cycling "gear", and, in my experience, the clothing, including shorts, is reasonable quality.
There is a "Special Buys Aldi" coming up in the next week or so, I believe.
In addition to the above, I recently purchased some cycling leggings and undershorts, for my (new to cycling, since lockdown) daughter, from
eBay. They were inexpensive, well under £50, and, I suspect may not last the year, but, they are certainly good enough to allow her to "try them out" and decide on which type she prefers, before committing to more expensive option (no doubt, on my credit card)
Links for the two products are
https://www.ebay.co.uk/itm/Women-Cycling-Tights-3-4-Shorts-Padded-Ladies-Leggings-Anti-Bac-Coolmax-Pad/262951314375?ssPageName=STRK%3AMEBIDX%3AIT&var=561957419488&_trksid=p2057872.m2749.l2649 and
https://www.ebay.co.uk/itm/3D-Padded-Men-Women-Cycling-Underwear-Bicycle-MTB-Riding-Shorts-Black-Soft-Pants/124014768788?ssPageName=STRK%3AMEBIDX%3AIT&var=424839016373&_trksid=p2057872.m2749.l2649, clearly, for my daughter, these are women's versions, but, they do have men versions too, I believe.