Start with the type. On a sheltered, level lawn a trampoline on legs is the simple answer. Where the site is open to the south-west, or looks out on the sea, look hard at the in-ground types, and have an installer check the ground before you order. Met Éireann gives the prevailing wind as between south and west.
Then the size. BERG asks for 2 m clear at the sides and 7 m overhead, on level ground, so measure the level part and take the clearance off. Then pick the range that makes that size at a price you are happy with.
A few notes on the tables. Clicking a price takes you to that model on TrampolinesIreland.com. Trampolines on legs always include a safety net. An InGround is offered both ways. Round FlatGround models have no net, and the larger rectangular ones can have a net or BERG's AeroWall stunt wall. Colours listed are grey, with one green, and BERG also makes black, so ask us about other colours.