It would be far easier to buy a cheap DVD recorder, some of the older ones, Analogue tuners, wih 250GB hard drive, can be bought for less than £40, this can then be used in connection with your Grundig receiver, and even be set to record programmes using the timer option.
The other solution is to buy a new receiver, either with a built in Hard drive, PVR, or with USB ports to connect an external hard drive. There are some reasonably priced satellite receivers, with these options, and some are HD.