MR Lite MDF Caberwood [UK] (Cheapest)
MR Lite MDF Medite [IRELAND]
MR MDF Kronospan [UK]
MR MDF Caberwood [UK]
MR MDF Medite [UK]
MR MDF Finsa Hidrofugo [SPAIN]
MR MDF Finsa Hidrofugo Plus [SPAIN] (Most Expensive)
As well as the above, you have imported products such as Guarafiber (Brazil), Capewood (China) and Intasa (Portugal). The imported products are generally good quality and will drop into the market when the UK price is high.
Hidrofugo, Hidrofugo Plus, Capewood and Intasa are all made with hardwood fibres or a mix of hardwood and softwood fibres which generally gives them better performance in comparison to UK produced boards which are made only using softwood fibres. The negative you'll get from these boards is they'll be heavier to handle/install.
As well as these you also have MR MDF Medite Plus (White Primed) which is a excellent primed finish.
TP and HG will likely have MR Lite MDF Caberwood, MR Lite MDF Medite, Guarafiber or Capewood. If they have Guarafiber or Capewood you'll have a good product for a good price but its likely you'd need to visit the warehouse to find out want. If you have a photo I could identify it for you.
Also, you may also want to consider everything apart from Medite and Finsa will likely be green dye throughout whereas Medite and Finsa will be sandwich core.