I’ve been doing a bit of plastic welding recently. I always used to use araldite in the past but it always fails eventually plus it looks a mess. All you need is a dremel (ideally) to scrape away any paint or previous repair material, a soldering iron and an old (or new) paint tray... avoid letting the solder iron get too hot, as long as it melts the plastic its hot enough, if it starts to smoke its getting too hot so keep turning it on and off to maintain the optimum temperature. Just press the iron into the crack and move down the cracked area using a prodding motion to fuse the area. If there is a gap or hole to fill just cut some filler strips from the black abs paint tray (available from your diy store for about 99p) and melt them into the repair. The repair will be very strong as you will have fused (welded) the repair. Then just sand down the area to finish the job.