Default [Q] Help with Huawei G300 Ascend U8815 - Running VERY slowly

I hope you can help. A long time ago I updated my wife's unlocked Vodafone UK G300 to Android 4.0.3 - I think it was the standard Huawei firmware and it has a Chinese splash screen. I do not think I rooted the phone though (since she had no need for those features). Settings tells me it is 4.0.3 baseband 2030 Kernel version 3.08.-perf-00245-gf3d97be Build number U8815V100R001C86B944 if that all helps?

Anyway, although the phone meets her needs in full it runs really slowly - I mean 1-2 second waits for most icons to respond. She is demanding a new phone which is reasonable but this seems like something I new firmware or clean up should sort. However, I have no idea where to start. She just needs a pretty generic firmware with nothing flash but that is responsive. Also I obviously don't want to lost all the apps and her personal data. Can someone please point me in the right direction. Although I have no idea what to do, I am confident in following rooting/jail breaking instructions and don't mind spending time on this. As a geek I seem to enjoy this kind of thing!

Thank you in advance.