...can i even take my bike on a train from london?
I'm guessing you're using East Midlands trains, in which case yes.
Strictly speaking, they only carry 2 bikes per train and you should make a bike reservation (you'll need to show your tickets for this), however in practice extra bikes can be carried at the guard's discretion and I never knew anyone to be turned away in the time I was commuting between London and Sheffield.
I'm guessing you're using East Midlands trains, in which case yes.
Strictly speaking, they only carry 2 bikes per train and you should make a bike reservation (you'll need to show your tickets for this), however in practice extra bikes can be carried at the guard's discretion and I never knew anyone to be turned away in the time I was commuting between London and Sheffield.