The press release for episode five is out, and the only truly interesting thing is that included in the guest list is "Fionnula Flanagan as Eloise Hawking."
This surely lends fuel to the "Mrs. Hawking is Daniel's mom" theory, seeing as our favorite rodent from "The Constant" was named Eloise.
A few ideas:
#1. Dan hates his mother and names lab rats after her.
#2. Dan loves his mother and named a very special lab rat after her.
#3. Mrs. Hawking, at least for a time, was also operating out of Oxford, was doing her own time travel work, and Dan gave the rat the name ironically, since they were both time travelers.
#4. Eloise the Rat is Mrs. Hawking.