aparantly if you have too many credit checks for mortgages (even if there all accepted!!) you can be given a black mark. What a crappy industry!
Whilst this used to be true, it isn't so much for mortgages.
When you have a credit check done it does leave a trail - the reason for this is if I was to lend money to you today, I would see a snapshot of your finances. If you had just applied for several credit cards you may next month have a lot more money outstanding than I anticipated. Therefore, if I know that you have applied for some credit cards I may make a different decision.
With a mortgage, you can only have one main mortgage on a property so the number of mortgage searches does not make a difference (although the number of loan / credit card searches would do)