I don´t know about the pricing on the parts themselves in the UK, but I do know this...
In late 1992, modifications were made to the C20LET engine - including a different cam belt and tensioners.
It´s supposed to be very easy to tell the two types of engine apart by checking the engine number.
However, in my case my engine number indicated that it was the NEW type, while in fact it was the OLD type.
At that point I had already bought the parts for the OLD type. Checked the engine number and found out I needed different parts so I had them exchanged.
So my semi-mechanic friend takes a look at the car and says: "No way I´m going to pull this thing apart, the part numbers don´t match and the length of the belt looks wrong too!"
At that point I decided to have the job done at an Opel (vaux) garage. And even though I had warned them that there was a question as to which parts would fit, they were VERY surprised to find that I was right and had to source the correct (old) parts while my disassembled car was sitting on the lift. Go figure....
In conclusion: Before you go ahead and buy the parts, make a note of your engine number AND the part number on your existing cam belt.
By the way, for some reason the parts for the OLD engine is significantly more expensive.
Do remember to have the water pump changed as well, it´s not expensive.
Oh dear. Even though its a 92 cav turbo, its had a new engine fitted about 15K ago. Makes things a bit more complicated doesnt it! Why change the water pump? It it fails isnt it just as easy to take the belt off and replace the pump, rather than cough up £100 for something i dont need yet?