MrsWhirling,
You mention 1.0 miles in your OP, now 0.7 miles. Which is it?
1.0 - equal to the furthest admitted child (under which criterion? It might e.g. be that siblings went out to 1.0 miles, but 'other children in order of proximity' only got to 0.2) is high risk, as catchments do shrink year on year.
Also check the general trend on furthest distance, and anything that might affect any major variations.
So for our local school, furthest admitted distance, non-sibling, started off as very large [relatively unpopular], then shrank year on year down to about 0.3 miles. Next year was 0.7 [but what you don't know is that that was a bulge class year, as otherwise the catchment would have been down to less than 200 metres for non siblings], next year to around 0.3 again, the year after that (the year most bulge class children had siblings) almost zero.
What you might want to do, to avoid the closer school being the one you have to as default, s check whether there is another 'virtually guaranteed' school, which could be MUCH further away but which you might prefer.