Preheat the oven to 392°F (200°C/180°C fan). Line a baking sheet with paper towels and set aside.
Pour the oil into a large roasting pan and pop it in the oven for about 5 minutes - or until it is very hot (like you would if you were making roasted potatoes). Tip the sausages into the hot oil and spread in an even layer. Pop in the oven and roast for about 20-25 minutes, or until golden brown.
Using a slotted spoon, remove the sausages from the pan and place them onto the lined baking sheet. This will help remove any excess oil.
Carefully discard any oil remaining in the pan. I use paper towels to wipe the oil out, as there shouldn’t be loads left, but if there is, just tip it carefully into a heatproof bowl and discard once cool.
Meanwhile, in a small bowl, mix together the honey and mustard.
Return the sausages to the pan and pour over the honey-mustard mixture. Stir well until all of the sausages are evenly coated.
Return the sausages to the oven and roast for another 5 minutes, shaking the pan halfway through, or until the sausages are gloriously golden and sticky. Watch closely to ensure they don’t burn!
Meanwhile, mix together the mayonnaise and wholegrain or Dijon mustard, to taste, in a small bowl. Set aside.
Remove the honey mustard glazed sausages from the oven and tip them onto a serving plate. Serve straight away with the mustard mayonnaise.