Wow, 549 GBP = $797 USD.
I can see the reason why you balked at paying that price, for just an LOF, plus the air filters, fuel filter and the spark plugs. Well, I would assume that they are including all of that along with the spark plugs, anyway.

Well, the spark plugs are definitely something you can do yourself.
All you need are the proper spark plug socket, a socket wrench, a couple extensions of differing lengths, and maybe a combination wrench that is the same size as the socket, and if you want to do the job correctly, a torque wrench to torque down the spark plugs.

And the air filters are also another item you can do yourself without any worry about fouling up the engine. They should be easy enough to procure from your local auto parts store, or I would be happy to buy a set of Purolator air filters up the street, slap a couple stamps on them, and send them your way.

That leaves the fuel filter and the oil change.
Some people don't like to muck around with those two systems, other people only dare tempt fate with one or the other. I personally enjoy doing both of them, and they are not too difficult, just potentially messy if you forget a step.

Anyway, if you can take care of several of the items yourself, you can greatly reduce the cost of the service by asking the dealership to only perform the tasks that you did not tackle yourself. Why pay someone else to perform work that you enjoy doing yourself?

BC.