The value of Hammond organs varies by several orders of magnitude depending on the model. The one in the original post is a later fully electronic spinet organ - you might get £20 for one if you're lucky. The M3/M100/L100 spinet organs, which are in the same form factor but have a mechanical tone generator and valve electronics, go for a few hundred depending on condition and features. The T100 - mechanical tone generator but transistor electronics - is also worth looking at but you don't see many of them in the UK. The full-sized, full-featured A100/B3/C3 are worth a couple of thousand, more in good condition - bearing in mind that even the newest ones are 50+ years old now.
That said, a lot of what people think of as the Hammond sound really comes from the Leslie's distortion and modulation, and even a cheap electronic organ sounds pretty convincing through a Leslie or a decent Leslie simulator... I went from an L100 + Leslie 2101 to a C3 + Leslie 122XB, and the latter is definitely better but it's not ten times better.