I'm in the middle of replacing the drivetrain on my bike.

I already have a Deore crankset and Deore LX rear mech (that I got ages ago).

I intend to buy the following;
HG30 7 speed cassette – to replace the 7 speed cassette that I have taken off
HG50 7 speed chain

will they be compatible?

Thanks in advance.

Yes, those two parts will work fine together.

When you fit the new chain there will be a black pin sticking out at the open end- you must join the chain with this, so shorten the chain at the other end to the same length as your old chain and join with the black pin.

That sentence will make more sense when the chain arrives and you see it in the flesh!

nice one – thanks for the quick reply.