I remember thinking that the extended title sounded awkward, and that Shang-Chi seemed an uncomfortable fit as he wasn't strictly a superhero, but over the weeks I grew to really like the series. Master of Kung Fu had only debuted in America a few months earlier, in Special Marvel Edition No.15 (which soon changed its title to Master of Kung Fu) but that comic wasn't distributed in the UK. (Not every Marvel comic was imported into Britain due to some limitation on distribution, although it did start coming through with later issues.)
The script was by Steve Englehart, one of the new wave of Marvel writers, with art by Jim Starlin who had already impressed fans with his early Marvel UK covers and his regular stint on Captain Marvel. The story concerned Shang-Chi being duped by his evil father (no less than the notorious Fu Manchu from Sax Rohmer's books) into killing an innocent man. Upon discovering the deceit and filled with guilt and remorse, Shang-Chi sets out on a path to oppose and destroy his father. Along the way, the strip becomes a spy thriller, with Shang joining British intelligence in their battles with Fu Manchu and his minions.
The original creators soon left the series and Doug Moench became the regular writer, with Paul Gulacy becoming the regular artist, and later Gene Day having a long run. It became one of Marvel's landmark series, with its creative teams raising the bar for more mature comics. Unfortunately the strip has never been reprinted due to legal snags with the copyright owners of Fu Manchu and its related characters that Sax Rohmer had created. Until now that is. Marvel recently announced that starting next summer they will publish four Master of Kung Fu Omnibus editions; huge hardback collections reprinting the entire series. Seems like any legal wrangles have finally been sorted out. The books won't be cheap though. The Marvel Omnis usually retail for around $100 each so start saving now!
Going back to the issue of Marvel UK's Avengers, this edition also featured reprints of The Avengers (natually) and Doctor Strange. As you can see, this was during the period when they thought adding heavy areas of zipatone / Letratone would compensate for the lack of full colour. Sometimes it proved effective but sometimes it obscured the art too much and was too distracting, as evidenced by the Doctor Strange splash page here.
The Avengers starring Shang-Chi, Master of Kung Fu remained the gobfull of a masthead for quite a while, and the Avengers part of the logo was even reduced in size after a few weeks. It was evident that Marvel UK felt Master of Kung Fu was the selling point, and I'm sure it was. However, with the comic being weekly, the Shang-Chi strips soon caught up with the American monthly. The solution was to create a few brand new 8 pagers that appeared in the UK edition first, which were then reprinted shortly after in America in Giant-Size Master of Kung Fu No.1. Presumably it wasn't financially viable to do that for long so the Shang-Chi strip was rested to enable more US strips to be generated. It was replaced in the UK weekly by Iron Fist, another Marvel kung fu hero, and yes, the comic's masthead became The Avengers starring Iron Fist for a while then too, alternating with it being The Avengers starring Dr.Strange, and simply The Avengers again. Marvel UK could be a bit messy like that back then, but that was all part of the fun.