Since updating my iPad , it has become much slower. It drives me mad at times.
But also it now takes an absolute age for it to charge.

Can I uninstall the update and go back to ios7?!

No, but iOS 9 will be out shortly and many people over at Macrumors running the beta on that device say iOS 9 feels more like iOS 7 did.

My iPad 2 isn't too bad. Have you tried a factory reset? That often fixes the slowness. Safari seems to suck regardless of the iOS version.

I have an iPad 2, and its has been fine on iOS8, it is on 8.4 now and is running fine.
Do not really see any Safari problems (not that I use it often), as I use the iCab browser all the time and that runs very well on the iPad2.
Really is worth clearing your safari cache now and again, Settings -> Safari -> Clear History and website Data.
Also if you use any newsstand apps, they often have a manual cache clear from within the app, that does build up.
But a restore to factory settings may help you and as long as you do a backup to iCloud it will bring all your settings and apps back after the restore.

Have been part of the iOS9 public beta and the iPad2 works well on there too. Seemed quicker in some respects, mainly the animations. Saw no problems, apart from a few apps were not compatible, but sure they will be on official release.

Six iPad 2's in my business along with some newer ones
ios 8 is good to go on all of them
Business specific apps too and all work as always have

Will iOS 9 work on iPad 2?

Yes. I'my running mine on the latest beta now and it runs fine, I'd say better than iOS8 for sure.

I've also been running the iOS9 beta on an iPad2 and it runs very well.

I have an ipad2 running ios 9.1Beta, it is better than 9.0, it wasnt great, after a full restore it has got better. Hopefully it will now last me another year.