Picked up 2 from my local Heron store yesterday.
Both extra mature and mature available for just £2 25.
Great value for a big block of quality cheese.
£5.75 on Ocado (site has picked this up as being available in Ocado for some reason)
https://www.ocado.com/webshop/product/Seriously-Strong-Cheddar-Extra-Mature/61026011

Description from the web.
Typically matured for 14 months and selected by our experts of its complex and tangy flavour

Seriously® Strong Extra Mature is our original cheddar made to a unique recipe for a wonderfully rich, tangy taste and crumbly texture.

Our award-winning cheese is only made using British milk in our creamery in Stranraer, Scotland, then selected by our cheese graders so you can enjoy the very best

This cheddar owes its full flavour to a lengthy maturation which can result in white spots on the cheddar and the presence of calcium lactate crystals (which give a tantalising crunch in the mouth). These are hallmarks of good quality and are typically found in the best quality matured cheddars.
Mc Lelland

This cheddar owes its full flavour to a lengthy maturation which can result in white spots on the cheddar and the presence of calcium lactate crystals (which give a tantalising crunch in the mouth). These are hallmarks of good quality and are typically found in the best quality matured cheddars.
Mc Lelland.

Suitable for vegetarians, A source of Calcium