Slime Smart Tube Exploded when I put it on mountain bike I bought a basic Apollo Mountain bike from a charity shop today - 

The only thing that seemed amiss was a flat tyre at the back.

I took care changing the inner tube and found the culprit a couple of thorns wedged in the tyre.

Anyway I was cycling soon after and heard a noise, looked down and then saw a bubble sticking out of the tyre, I stopped straight away but it was too late - with a loud noise the inner tube exploded.

It's damaged the tyre to the extent that the metal wires on the rim of the tyre were now exposed where it had burst out.

I popped the old inner tube back in wondering if this would now be a slow puncture now that the obstructions were removed, just hoping to be able to push the bicycle home at this stage.

The exposed damaged bit of the tyre on the very edge of the rim of the tyre was placed behind the metal bit of the wheel.

I pumped it up and a small bit of the inner tube is bulging out near the rim, I was able to push it home at least.

The bike looks as new and apart from this damage to the one tyre they are both otherwise in perfect condition.

I'm fearing the worst that I'll have to buy a new tyre, if so will it have to be a 26x of the same design? Is there any way to patch up a small part of a tyre?

What did I do wrong here,is it possible I over inflated the slime/self repair tyre? It was a very impressive exxplosion/implosion anyway.

Thanks for any tips
I can think of three scenarios that caused your issue. The tire was damaged from running flat before you got it. While installing the new tube it was pinched between the tire and rim. After inflation it lifted the bead off the rim resulting in both the tire and tube failing. The tire was grossly overinflated resulting in the tire sidewall and bead separating.