I doubt anyone will be able to help but you may be lucky.
This is a North American site so I do not have access to tech info on European units.
I do not know what it is like in the UK but in North America manufacturers do not publish board schematics.

You give the number for a "neighbouring TRIAC" so I am assuming you cannot get a number off of the bad triac.

Googling just Z7S should get you some info on the triac you list.

Then you will have to decide how big a gamble it is to assume both triacs are the same.

Sorry I could not be helpful.

see attachment

I cannot say if something else caused it to blow.
Without a schematic this may be challenging.
You will have to trace the copper tracks to find out what the triac controlled and then check that part to see if it is defective.
G is the gate and A1 and A2 is power.

It of course has to be the same physically.
Then Google using the Z0i07SN number.
Disregard sites that just give you a data sheet and choose site that actually sell electronic parts.
They should give you basic part specs and with luck perhaps a couple alternatives.

Now you are stretching me.
I have not messed with component replacement for over 20 years.
I was in laboratory instrumentation and they even went to board replacement instead of troubleshooting down to component level.
In most cases it was cheaper for a customer to replace the board than pay for my time to troubleshoot down to the component unless it was something obvious or a known fault.

I never had to mess with part specs if I could not find a cross reference locally I could always order from the company I worked for. So I have not really looked at component specs since I left college and that was about 40 years ago.

I did find this on the net that looked like a decent explanation.
http://www.google.ca/url?sa=t&a...2eMgBcXOmEmg&cad=rja