Telestial has a product:
http://www.telestial.com/view_product.php?...CT_ID=MSIM-PP01
Yackie mobile (see link above) also has a UK mumber. It's a land line though which should be cheaper, but there is no free incoming call anywhere. You can also check the thread hare about yackie mobile.
http://www.prepaidgsm.net/forum/inde...showtopic=1211
Phones: Xiaomi Mi Mix 2, Samsung Galaxy A50, ASUS zenfone 3,
Sim cards: AT&T (Contract), 3 UK, Piranha Mobile