Ok,
for anyone that is interrested, or didnt already know, I have done my homework on the two shampoos listed above, and the difference is that:
Nizoral has active ingredient Ketoconozole 2%
Nizorelle has active ingredient Ketoconozole 1%
and there is an obviouse price difference of nearly Half for the 1% compared to the 2%
Also boots have their own brand of dandruff shampoo with Ketoconozole 1% which in turn costs less than Nizorelle
Jai