Hi Andy,
Its good advice from Ed, try 2 units less with your toast and then test afterwards to see the results, remember to test every hour up to the 4 hour mark. I notice you were taking the same amount of insulin (10 units of actrapid) at every meal previously, so I take it that you were eating carbs to suit your insulin dose, as opposed to matching insulin to the food you eat.
Should this be the case Andy, have you tried the DAFNE course, they teach you to match your insulin to the food you eat. Its a 5 day course, very worthwhile and teaches you how to count carbs, dose adjust, sick day rules with insulin and loads more. I had type 1 for 27 years before I enrolled, but believe me, it was one of the best things I've done!
I would suggest you get in touch with your diabetes clinic, speak to someone about your present problem, even enquire about the course if you have not already been on it.
Good luck
Nigel