I want to avoid Halfords if possible! Unless they are the cheapest?

Did you try using google?

 

Bosch Aerotwins start at about £18.50 for the front pair:

- https://www.amazon.co.uk/Bosch-A937S-Aerotwin-Wiper-Blade/dp/B005FW4RA2

- https://www.ebay.co.uk/itm/201554111084

 

I'm sure other brands/suppliers might be cheaper.

http://www.windscreenwipersdirect.co.uk

 

Another vote for Amazon or Euro Car Parts as they usually have anywhere from 40-70% off discounts. 

Costco do cheap Michelin wipers if you have costco membership