Will it affect my credit score?
Lenders will run a credit search when issuing agreements in principle. Most will do a hard search, where the search is visible to lenders on your credit report. Other lenders will do a soft search, which lenders will not be able to see on your report.
Too many credit searches in a short period of time will negatively affect your credit rating. While purchasing a house you are only likely to receive one search, so this is unlikely to be an issue