WHBM, thanks. That is a very helpful reply.
The
Thameslink makes me much more mobile towards London (22min to Kings Cross is alright for a daily transfer) where I have a much better & broader choice of hotels. A colleague already stayed in one of the Holiday Inns. He started to transpire when I asked him about the property ... not good.
The connection from LHR looks also quite easy.
My destination in Borehamwood is around the Elstree Tower. (On a map it looks like almost twice the distance to the film studios. I guess that the walking time is around 30min.)