A 5mm section update [member=179432]ojfarmer[/member] - you might have progressed with your irri' system planning by now, but thought I would offer the following: I put just 100-150 ltrs of water into IBC for apple beds today for a quick dollup of liquid fertilizer via the 5mm irri' section. Overall head of water no more than 1m at best: by the time I'd shuffled 10 paces or so to the plot, all drippers were dripping (55 drippers on this occasion - I won't bother explain why I added a 5 dripper leg to my 2x25 dripper sections). I paid a bit more attention to overall drip rates than usual and I would say there wasn't much difference across the section with all drippers pretty-much set for minimum drip rate. (Of course, flow rates across a section can be adjusted, if necessary, by tweaking individual emitters.)
Otherwise:
Another good-price find. Tesco's supply of £0.50 hose connectors has dried up here (pun intended LOL). Needing a few more (for permutations), I found Homebase offer an Aqua Systems brand at £1.00 a pop for the various standard types of hose connector: they seem to me to be better made and worth the extra. Also, Aqua's tap-mounted hose splitter (with valve control to each leg) costs just £5.20. It's a solid bit of kit! Go compare the £1.00 and £5.20 prices to better-known brand prices (on the Homebase web-site or any other) and then go pick up some Aqua Systems connectors (assuming you have a Homebase near-by)!
My verdict on Fitt NTS Wintech garden hose: it is indeed, as cloddopper said, the "dogs B.....s". Worth every penny even if you can't buy at Screwfix's price.