While my current cheapie phone (a Redmi Note 3) has working band 28 support, the later versions dropped that.

I've found another phone with band 28 support, but it is listed as having LTE bands 28a and 28b support. I hadn't heard of the range being divided before - it looks like they've kept the standard 700MHz upload and download frequencies, but divided them up between 28a and 28b - 28a has 703-718MHz, and 28b has 718-748MHz UL, while 28a has 758-773MHz and 28b 773-803MHz DL.

I assume that because the whole range of frequencies is covered it shouldn't have an issue with the Vodafone 700MHz network?