It’s all a bit of a homage to the 1966 film; Fantastic Voyage but it is perhaps most fondly remembered for being the story that first introduced K9, The Doctor’s much loved robot dog. Or disliked for exactly the same reason depending on how you feel about the metal mutt.
Thinking about spacesuits in Doctor Who, I had forgotten about this one but once remembered I have to say that what we see on screen is rather splendid and actually looks like they’ve had a few quid spent on them.
It also looks like elements of this suit were used again in the Blake’s 7 episode; Voices of the Past a couple of years later. There's a blog post so go check it out.