Nilesat is at best marginal in the uk. Theoretically we shouldn't be able to get it at all, but the sats are performing better than expected. All sat signals are absorbed to some degree by cloud cover / rainfall, So in the case of ultra marginal signals, any thick cloud cover will kill the signal. The sats also move around a little every day, not important when you are under the main footprint, but it can make the difference between pics and no pics for extreme fringe reception.
For better signals, you need a bigger dish.