Wilko garden swing seat drink holder

I designed this thing to hold a cup or glass on a Wilko (UK) 3-seater garden swing seat.
Although the swing was bought in UK it was made in China so is probably available in many other countries under different brand names. The tubes in the swing frame are about 48mm diameter and the holder is designed to clamp onto the curved tube at a position where the tray portion is approximately horizontal. Arranging it to have a very slight downward slant will allow any rainwater to drain from the hole a