Tesco have the Plum 8ft Trampoline with the enclosure for £79 reduced from £149. This trampoline is £134.99 at Boots, and £159.99 at Outdoor Toys Direct, so it's a pretty good price. This is free on click and collect but to be honest I'd pay the extra £3 delivery so I don't have to drag it all the way home! Use the code TDX-PNTY for 500 Tesco Clubcard points, which gives you £25 back, or if you're a first time shopper, or want to use a new email address, the code TDX-PRKW brings the price down to £69.
This 8ft trampoline with enclosure from Plum Products is designed to keep the user within a safe area, thus reducing the risk of falling. The frame is made from steel galvanised inside and out for rust-free protection and increased strength. The 42 high quality zinc-coated steel springs ensure extra durability. The jumping mat provides excellent bounce performance, and the weather protected foam pads provide safe cushioning.
It's suited to children or lighter adults - the maximum capacity is 75kg, although Tesco say it's suited to a 5 - 8 year old, so I think there might be space and allowance on it for two.
Now that would be a fun summer activity.