Character mistake: Gaz is reading a magazine. It is not a real magazine, except within the storyline. There is a full-page picture of Johnny and the headline "Competion winner".
Continuity mistake: During the scene with Donna, Louise and Janet in the kitchen getting ready to go out, they are talking about the valentines cards and how she only got one from Louise and herself. However in a previous season after Janet kisses Andy, we are told that Janet and Andy were together when Janet and Jonny first met.
Plot hole: Tim says to Donna and Gaz that Janet asked him to find new tenants for her house when she moved to Milton Keynes. But in S7E6 "Six Months Later" Donna agreed with Gaz to buy Janet's house to save her house getting repossessed, so by rights Donna and Gaz could have moved in there without the help of Tim because she owns the house. And apparently Donna has had to sign on in series 9, but she could have sold Janet's house after a while of living there if she didn't want to live in Janet's house for the rest of her life with Gaz.