Flashing coil light?

Brought the car last week seemed okay driving home didn't drive it for 2 days while sorting tax and insurance.
When I did then drive it had a very rough engine and smoke from exhaust (has been very cold here) stupidly I got it from a private seller lesson learned! So, I took it to my garage, the only fault he could find was cracked fuel filter casing. Have had that fixed (£240.) Collected it yesterday as the garage was closing. On my way home I noticed the coil light (glow plug light) flashing! There was some smoke still but there wasn't any when I started it this morning. I haven't driven it yet and my garage is closed until Monday, but I need my car tomorrow. It's still flashing engine does seem to be running smoother now fuel filters done and starts first time. Any advice please.