Hi , the Circlip ends broke off when I was trying to remove the steering box bottom seal in situ . I'm at a loss as to how to deal with this . YouTube hasn't been much use .. all help welcome .

Which vehicle?

ETA Quick look at your profile suggests it's a Defender 110.

Done this a couple of times in situ on my RRC (4 bolt box), but the circlip behaved itself after a bit of cleaning, lubricating & tapping. Last time I used the blue seal & put a speedisleeve on the shaft.

Your old clip will have rusted into position. It MIGHT be better to remove it to make life easier & do it on the bench/in a vice as you can turn it upside down.
You're going to have to use a pointed pick to try & get the remains out. One with a right angled tip.
Good soaking with Plus-gas or similar & use a screwdriver blade to tap what you can get at of the circlip surface (as you look at it from the bottom) to help release it from the rust.
Problem is that there isn't much room. If that doesn't work then you'll need to remove the shaft.

Ratae , it's a Defender 300tdi . I'm hoping to deal with it in situ .

I don't know which box you've got on yours, but there's a 'how to' showing the dismantling of an adwest lightweight here:
www.youtube.com/watch?v=xXQIsfBBhkk

Ratae , it's the four bolt Adwest .

Worth watching the video.
Hopefully you'll manage to get it out, but plan for 'worst case'.
TBH I've not found taking mine off that much of a problem & bleeding was straightforward.
I also replaced the input shaft seal in situ.