Stumbled on this.
If you have a Virgin credit card, you can get an additional 10% off this making it £100.80. Looked for code on Virgin members shop and maintenance being done. Will update the post when it's up.
Series 6 is released on 5th Nov, cheapest being £31.99. All other series are around the £25 mark.
Works out at £18.66 for each series without VC card or £16.80 with a VC card.
Virgin Megastore no longer on Quidco unfortunately for even more savings. :(