Thanks for that. I hadn't appreciated the fact that the NAS could be used directly and was assuming we would use a box in the same way as we do with the Humax. Record and play stuff directly, but archive anything we wish to keep to the NAS. I could buy a relatively small micro SD initially then. The 'sweet spot' for pricing seems to be 128GB or 256GB - 64 isn't much cheaper than 128 and 512 is a lot more than double a 256.
I wasn't suggesting the AX company was in any way less respectable, simply that a new product from any manufacturer may have teething problems which nowadays get sorted in 99% of cases. I suppose we all remember stuff delivered with rubbish firmware that never got fixed and you were forced to live with it or bin the product.