Looks okay Muddy, but its all about how well you put them together and secure them to the ground. We used to dig a 2' trench alongside, set the frame down into it and bury the foot of the poly. They were big commercial ones at Blooms of Bressingham though.
This looks flimsey and will blow away and not last long. attached is one I built at my uncles and have since built my own. what you need is 4 foot scaffold poles, 63mm gas or waterpipe, roofing laths, and a plastic cover sheet.
hammer the poles 2 foot deep in the ground at 5 foot intervals for each side and as long as you want it then match it on the othetr side as wide as you want it leafing 2 foot sticking out the ground. measure and cut the pipe to form an arch so it ends up about 6 foot high at the highest point, slide the pipe over the scaffold pole ( this will fit exactly over the pole), use the roofing laths to build a skeletal frame keeping them on the inside and also scre into the thick walled pipe from the inside. this is so when you measure and buy your sheeting it does not rub on anything sharp and rip, pull it tight over the frame and fix each side to more planks at ground level. finally build a frame on either end so you can open them both when it gets very hot.
you will be amazed how much you can grow, even in winter grow spinach, cabbage etc and dry your cloths in here, bring some big plants in out of the cold., I got the pipe for a tenner of some waterboard contrcators as they were too short for them to use, buy the laths from aroofing contractor, about 20 quid for 15 4.8m lengths, the sheet is from online polytuinnel company £60 but is coated so condensation does not drip down onto plants that rots them.
Here is one off youtube which explains more although this guy is using 50mm pipe which has split over the scaffold poles ( my scaffold poles are 53mm outside diameter and the plastic pipe is 63mm internal diameter
Use more laths than this dude and make it more sturdy and it will last, mine is still going strone since 2007
when its raining outside you can also get your deckchair and chill in here with a bottle of wine, the radio on with a good football match and put your feet up for a few hours. while your wife is cooking the sunday dinner thinking your hard at work tending the plants.