Not a bad beginning only thing I could fault you on is that mrs figg probably wouldn't know most of the stuff she said in her letter to dudley. You might want to find a different character to write the letter. You could have mrs figg contact the other perdon and have him/her write it.
She does say sge had to check some things. It is assumed in HP canon that she must have had some way to speak to Dumbledore re Harry; and although never mentioned in my story I assume the information came that way.
Hope this helps. Please ontinue to read and hopefully enjoy as i post