Which Tesco was it out of interest? The Metro at Kensington had one similar to this:
http://www.ingenico.co.uk/en/products/payment-terminals/retail-pin-pads/ipp300-series/
And that worked fine.
It was one in Bermondsey (on Southark Park rd - a small Tesco Metro)...
I completely agree newer terminals seem fine, but ones like this aren't working for me:
http://www.datacard.com/images/products/id-product-detail/encoder-ingenico.png
Even though they show the 'contactless' symbol.
Any ideas?