Another vote for halfords tools, does the forum still do discount cards? Which makes them even better value. I bought a good set of allan keys some while back whose name escapes me, which have never rounded off. I would always get the best hex keys you can find makes life a lot easier.
PB Bauman, Swiss Tools Allen keys are one of the best for not wearing out. They have out lasted Beta and Bondhus keys. https://www.pbswisstools.co.uk/catalog/PB_Swiss_Tools/PB_211_H.html
Any good quality tool will do the job, just make sure the one you are using is a good fit. If there is doubt about the materials used for the fasteners, a good tap on the head of the screw will help to free it off, as already stated replace with at least 8.8 grade screws, tightened to the correct torque. Oil or grease on the threads will increase the torque, charts showing dry and lubed settings are available on the internet.
