McVities Ginger Nuts before they changed the recipe and made them softer and more likely to crumble into your tea when you dunked them.
Huntley & Palmer's Lemon Puffs – the most exquisite of biscuits; I never did understand why they were discontinued.
I seldom buy biscuits any more and when I do it will be when I am expecting company and they will be quality ones, Dark Chocolate Gingers and Sultana Melts from Border Biscuits of Lanark or (be still my beating heart!) Lemon Melts and Apple Crumbles by the Island Bakery of Tobermory– this isn't out of snobbery or even loyalty to my adopted country but because I know if I buy any biscuits for myself I will eat them in short order.
My philosophy these days is less but of better quality of things that are bad for me. The upside is that I find I actually want less of the quality product. Just as I can scoff a whole packet of custard creams, if I buy myself a Galaxy bar as I used to almost daily I can't just eat a few squares and put it aside, it has to be the whole bar. I know what it is, it's the sugar not the chocolate that is "moreish" (ie addictive) and if I buy myself a box of 14 Hotel Chocolat 70% batons I can easily restrict myself to one a day, so that works out a lot cheaper than a Galaxy bar a day. Same with cheese, to which I actually have a slight intolerance. I no longer buy mousetrap unless I want it for cooking because I'll happily nibble away at it until it's gone, but if I treat myself very occasionally to a small amount of something exotically pungent from Mr Mellis's or Mr Mew's empororia that will make me very content!