>Yearly thousands upon thousands of animals are rescued, £150,000 was raised over 43 “walkies events” in 2016 and much more.

The problem with this sentence is not the use of "much much more", as a phrase, but the fact that you have a list with 2 items and then are trying to add a third item to the list which means "also there are a lot of other things".  No matter what phrasing you use, this will be unclear.  

It's not really a list, it's 2 things that you're trying to inflate.  Because of this, it's not really clear it's a list, and the "and much more" looks like it applies to one single item in the "list", not the list as a whole.

Also, mixing a general achievement "per year" followed by a specific number for a specific year in the same list makes it confusing to read, and so this makes the "and much more" even less clear.

For these reasons, I have chosen a different phrasing to imply "also, there are other things".  *Among the ____________*  allows you to specific to what you are referring.

>Among the many achievements of the RSPCA, are the thousands upon thousands of animals rescued each year, and the revenue generated by fundraising events.  For example, £150,000 was raised over 43 “walkies events” in 2016.

Note how I have split the general and the year specific examples apart too.