Thinly slice the steak. On a clean board, peel and finely chop the garlic for the steak.
In a large bowl, combine the garlic, lime juice, Worcestershire sauce, chilli powder, oregano, cumin and black pepper then add the beef and toss until coated. Cover and place in the fridge.
Make the guacamole. Peel and finely chop the onion, and roughly chop the coriander.
Peel and finely chop the garlic. Slice the avocado in half and remove the stone.
Spoon out the avocado flesh into a bowl. Add the garlic, olive oil, lime juice and tabasco and mash with the back of a fork. You could also do your mashing in a pestle and mortar if you wish!
When you have a rough mash, add the finely chopped onion and stir through the chopped coriander. Season well with salt and black pepper. Serve within an hour of making.
Next work on the fajita prep. Peel and thinly slice the red onion and slice the peppers into thin strips.
Chop the coriander for the steak. Grate the cheddar cheese and set aside.
Heat half the sunflower oil in a large frying pan over a medium heat, add the onion and peppers and fry for 3-4 minutes until caramelised. Set the vegetables aside in a dish.
Add an extra drizzle of oil to the pan and fry the marinated beef for 3 minutes until cooked but still tender. Make sure the pan is hot before cooking the beef.
Add the reserved onions and peppers and the coriander, season with salt to taste and stir through. Heat the tortilla wraps in the microwave for 40 seconds and cover with foil to keep warm.
To assemble, spread a little guacamole on a tortilla, add some steak, peppers and onion and then top with sour cream and cheese.