I'm very surprised to read that a tape system should be recommended for foxes. This sounds like very bad advice. You not only need to keep foxes out but you need to keep chx in. A tape system is only any good for larger grazing animals like horses. A net is the usually recommended system for chickens and foxes. They will cost a bit more than tape I'm afraid but they will work effectively.
I've always used electrified runs and never lost a bird which was in one in over 10 years however you must use an electric NET. The best ones are 1.22 metres high and I'd recommend the Fox Buster type from Electric Fencing Direct
http://www.electricfencing.co.uk/electricnetting.asp Nets are powered by an energiser. Get a reasonable output one say 1.2 joules. The Hotline Gemini HLC 120 one is OK at a reasonable price (as is the Force Field BM 140 one below). Lower output ones are slightly cheaper and run for longer on a battery but are more easily shorted out by long grass/ weeds and rended ineffective.
http://www.electricfence-online.co.uk/shop/electric-fencing/energisers-mains-powered/12v-mains-hotline-hlc120-gemini-346433.html.
Shop around on ebay but buy new as they are still expensive second hand and can be damaged by misuse so a guarentee is important.
Energisers should be powered off a rechargable 12V LEISURE battery or they can be powered by a mains adapter if there's a convenient mains supply. Beware, some use a 9V non-rechargable battery and require a special dry cell battery. These are light weight and intended for easy carrying in fields for setting up portable enclosures. Unless this is what you want use a 12V lead acid battery which MUST be a leisure type as car batteries are very quickly destroyed by deep discharges. LEISURE ones are designed specifically for deep discharges (shop around on ebay and get a 60Ahr or greater one which will last 4 weeks plus on one charge.
You will also need an earth stake which you can buy though any metal rod about 600mm long will do. On one of my nets I actually use an old broken garden fork pronges driven into the earth with a club hammer. I clip the earth lead to the metal shaft. Keep the earth damp around it.
Rough budget assuming new buys.
Leisure Battery £60 ( I recently bought a 65Ahr redundant stock new one for for £40 off ebay which was excellent quality)
Charger £15 - £30 (the cheap ones are rubbish generally)
50 m Net £120, 25 metre ones are a little less expensive but not half. Don't skimp on this item the one I recommend is a little more expensive but much more robust than the cheep alternatives available.
Energiser £90.
6 tree stakes (assuming you use a "figure of 8" folded layout) £16
Consider a kit from Electric Fencing Direct which might be more cost effective though the battery & charger isn't usually included
Below is a cut and paste of previous advice and some links to electric net threads.
You can cater for the excess by folding it but make sure it's off the ground otherwise it will short. Use tree stakes at each corner to attach the plastic insulated posts to (they mustn't touch so guy them off with plastic/ nylon cord baler twine is fine. Tension the net tightly and have STRAIGHT runs between corners and ensure each corner is supported with a tree stake. The surplus can be loosly folded and helg off the ground, or insulated from it by laying it on a polythene sheet, or large poly bag, or in a plastic tub or anything which is plastic or rubber so it's insulated from vegetation and the ground.
These topics are mostly covered in the second link below.
http://chat.allotment-garden.org/index.php?topic=68573.msg784480#msg784480http://chat.allotment-garden.org/index.php?topic=56897.msg670192#msg670192http://chat.allotment-garden.org/index.php?topic=25998.msg307988#msg307988http://chat.allotment-garden.org/index.php?topic=32823.msg392728#msg392728http://chat.allotment-garden.org/index.php?topic=43809.msg514210#msg514210http://chat.allotment-garden.org/index.php?topic=42658.msg502557#msg502557http://chat.allotment-garden.org/index.php?topic=51867.msg616566#msg616566http://chat.allotment-garden.org/index.php?topic=59656.0HF