Thats it, I remember paying about £40 too. You can use the one thats already on there, but it wont be calibrated to those dials as such. Thats how my set up works and its been fine. It might not read 100% accurate on the dials, but I know where the needle sits normally, so if it raises any higher than that, I know I need to be weary of the temps.
You can get a VDO temp sender from them too but it sits in replacement of the sump plug. I think id rather know the temps of the oil in the filter housing since that should give me a reading of oil temps coming out of the block