We ended up going to a local PC store today so my mother could physically examine the printers. I will give a brief run down of the printers we looked at, it may help others with their choice.
My mother had already decided that having an SD card was now a must rather than a nice to have.
HP
The store had a decent range of HP MFP's however none of them had all the requirements. They were missing either one or two different requirements. For example, one had 4 colour inks but was lacking the SD card slot, where as another had all the requirements but the coloured ink was in a single cartridge.
The build quality was pretty solid across all the models and the prices were roughly similar with a rough average of about £120.
Epson
It looked like the store had quite a range of Epson printers, many in budget or under. I tried to insist that we should at least look at them in the interests of fairness but was over-ruled. I am only mentioning them here as balance.
Brother
There were two Brother devices that met our requirements apart from build quality. The display models looked shabby and flimsy, especially considering the prices of them were quite high. That said they both made our shortlist because they could handle A3 paper. They were eventually discounted as we felt they would not stand up to regular use.
The models we considered were:
Other
The store we went only had a single Samsung printer and a single Lexmark printer available. The Samsung did not have an SD card slot and was well out of budget and the Lexmark was a standalone printer with no scanning capabilities.
Canon
I have left Canon until last as we ultimately ended up getting a Canon device. The build quality of all the Canon's, even the sub-£50 ones, was excellent. On a similar par to HP.
We were also hugely impressed by the design philosophy that had been followed on the mid-range printers, they looked "unprinterish".
The two that made it on to our shortlist were:
These are almost identical printers but we ended up choosing the Pixma MG6851. The things that swung it were the fact it was on sale at £80 and the fewer inks. My mother was concerned that the extra "grey" cartridge in the MG7751 would make the ink more expensive in the long run, even though she preferred the minimalist look on the MG7751.
