@Shortysoso
YANBU. It's not just Superdrug either. The shops 'Bodycare,' AND 'Savers' ask me EVERY TIME I go in to get antihistamines or a bottle of talc or some shower gel, if I want Britney Spears latest perfume, or a set of David Beckham smellies... And WH Smith ALWAYS ask if I want to buy a nearly-out-of-date Terrys Chocolate Orange for £1.50, when I am going in to buy a magazine.
And many other shops do it too. My local little 'paper shop' does it... tries to palm off 'nearly-out-of-date' chocolate onto me... Or asks if I want some stamps or phone credit... Every time!
Even when I go to buy a stamp, the post office asks me if I want their insurance for my car/house/life, and keeps me at the counter for 10 minutes. It's as annoying as the irksome 'do you have 5 minutes to do a medicine review' bollocks that Boots always do. (And some other pharmacies too!)
Claires Accessories used to do this too (Although I haven't shopped there since DD was about 14 to 16, so over 10 years!) We would buy 2 or 3 items at a cost of £10 or so, (say 2 pairs of earrings and a bangle,) and they would say 'would you like to purchase a mini turtle purse for just £5.99,' or 'would you like to purchase a 3 pack of lip balm for just £4.99?'
Clintons and the Card Factory try and upsell at the till too. Often a pack of 3 pens for £3.00, or a notepad and a pack of envelopes or something! 
And although this hasn't happened for some 10 to 12 years, (as I haven't shopped at either one since then,) I used to get SO pissed off with BHS, and Debenhams ALWAYS trying to palm a storecard off on me. I said 'I don't so storecards..'
One assistant said I was 'very silly' for not having one. I thought that was very fucking rude. I was so close to complaining about her, but couldn't be arsed to hang around. After that, I never went into a Debenhams again, and BHS closed down soon after.
I HATE upselling, but I know it's not the shop assistant's fault, so I don't get arsey with them; I just politely decline...
Like many others on here, I tend to avoid most of these places now, and get as much stuff as possible from B & M, Wilkos, and Home Bargains, or Tesco/Morrisons/Asda/Sainsburys, where they don't try and 'upsell.'