It would be cheaper to buy new stuff from China than to post you stuff from the UK.
Brave Person swim bikinis and thongs are unlined, really brief and quite affordable, have a look:
https://www.ebay.co.uk/itm/Brave-Per...-3BDFNDxty_68Q
If you preffer something lined try Desmiit, swim bikinis, briefs and thongs, still pretty sexy though:
https://www.ebay.co.uk/itm/Mens-Low-...mvR6 ODprC8vQ
I rather like these, it says Addicted but I think they are made by Eussienq if you'd preffer a 2" side sexy suit, you'll enjoy how the front pouch moulds to your body:
https://www.ebay.co.uk/itm/Mens-Swim...iyV_ SbhGl41Q
If you feel both cheap and patriotic try these:
https://www.ebay.co.uk/itm/Mens-Summ...de820fc81b7f3e
PS These are sexy and I love them, I have a pair of the wolf ones:
https://www.ebay.co.uk/itm/new-Men-U....c100005.m1851