Probably been done before, but think I have now worked out how to do a DIY laser alignment check. Thought I would post in case it helps anyone.
1. Required items 1 laser level (about £5 on ebay) and 1 long spirit level (although anything flat and dead straight would do).
2. Make sure the bike is vertical then hold the long spirit level against sides of tyres with the laser. Fairly high, just under the disc.
3. Align laser against garage door / wall whatever as far ahead of the bike as possible. Mark vertical line with chalk on the garage door / wall, spin wheel and check mark is still correct.
4. Then repeat above on the other side of the tyre, (so you have two vertical chalk marks on garage door)
5. Finally, use the level aligned dead straight ALONG the bike - I used fuel filler cap and centre of luggage rack as guides. Place laser on the top at the level shining along the length of the bike, as below, and mark the vertical on the garage door as below. This chalk mark will be higher up but if it is central (vertically) between the left and right marks then the wheel is aligned.