Hi ChippyB, just thought I'd answer based on my own experience and what I've seen elsewhere...this might not necessarily be true in your niche, or for your site…
Anyway, I have had a couple of sites where I have seen improvements that were seemingly based on +1s (although impossible to say this was definitely the reason) and the jump is usually 1-2 positions. This is often dictated by how many +1s competitors in your niche have as well – you said '70' in your example, but this number might differ depending on how active your competitors are on G+. This has also been evidenced by a couple of other webmasters I have spoken to who have said they have been able to improve 1-2 positions in the SERPs by getting more +1s.
I would be careful about gaming this though, as it's easy for Google to spot when a profile is being manipulated. You only get 30 visitors a day, then suddenly you get 300 +1s…it's likely to trip a filter in the algo. Same if you have only got, 70 Facebook fans, for example, then suddenly you get 500 +1s, it just looks unnatural and might do you more harm than good.
So yeah…if you are going to try and increase your +1s, just take care do it in a way that appears natural...or just get +1s naturally in the first place
Anyway, someone else on the forum might have had a completely different experience, but this is just what I have found! Hopefully it works for you anyway
