I've got quite a few:
Man - A truly great progressive rock band which released many wonderful albums including 'Do you Like it Here Now, Are you Settling In?' There were a number of spin-offs, including Iceberg, Clive John's solo work and Neutrons;
Deke Leonard's Iceberg - More Man than Man;
Clive John - Man solo;
Neutrons - Man spin-off band;
Budgie - One of the best heavy rock bands of all time, with crunching riffs, weird song titles and Roger Dean imagery;
Dave Edmunds and Rockpile - Released a famous version of 'Sabre Dance' (as Love Sculpture) in 1968, followed by an unpretentious version of 'I Here You Knocking' in 1970. Edmunds went on to be a successful producer;
Racing Cars - One hit wonders for 'They Shoot Horses, Don't They?' in 1977, despite being signed to Chrysalis, supporting Bad Co on tour and having a strong live following;
Sassafras - Released three excellent albums (i) 'Expecting Company' 1973, (ii) 'Wheelin' 'N' Dealin' 1975 and (iii) 'Riding High' 1976. The second includes a superior version of Neil Young's 'Ohio';
Tigertailz - Their best album is 'Young and Crazy' from 1987, with 'Livin' Without You';
Tredegar - Featuring Tony Bourge of Budgie;
Bonnie Tyler - Had a hit in 1976 with 'Lost in France' before working with Jim Steinman on the 'Faster Than the Speed of Night' album (1983) which produced the 'Total Eclipse of the Heart' single.
Not my favourites, but Welsh:
Shirley Bassey
Tom Jones
Shakin' Stevens
Manic Street Preachers
Catatonia
Super Furry Animals
Weird:
Welsh Elvis impersonator Peter Singh and The Screaming Pakistanis