If I bought some sapplins say 30 or more, would it be possible to start my own patch of phalaris. Ive read phalaris will grow pretty much anywhre exept antartica, so by that statement alone it should be fine, but I wanted to double check on here first.

If it's not wild in your area, it could become and or be considered invasive.

Yeah I did read this somewhere, what about as a back garden project, would it grow well enough in northern uk climates, also how much plant matter would i need to do an extraction that would be worth my while growing, harvest etc
thanks

Yes it should be naturally and locally available near you.
Phalaris Arundinacea is what you would look for and there are MANY threads regarding identification, safety, and extraction methods for this grass. I would take the time to read through as much as your mind can comprehend, for it will pay off.
Phalaris is a viable plant to work with as a powerful teacher and you'll learn that it offers a rather different lesson than many other tryptamine/beta carboline containing plants. A pangean entheogen, it contains unique MAOI beta carboline alkaloids found in Anadenanthera Peregrina, Acacia Simplicifolia and phenethylamines found in Trichocereus cactus species, as well as the desirable DMT and 5-Methoxy-DMT(many times among other tryptamines such as 5-methyl-tryptamine and 5-Methoxy-NMT, occasionally providing traces of 5-Hydroxy-DMT). A brew decoction similar to the preparation of Ayahuasca would suffice for effects. Precautions should be taken. Patience as well.
Growing enough grass to perform a full extraction would call for anywhere from 1-5 grams of seeds.
Clones are a a better option though I would wait to grow out a ton of grass and give an extraction a go with bioassay before discerning what plant's rhizomes need to be divided.

The clean-up phase(defats) turns many away from seeking the medicine the grass has to offer.
Certain techniques will for the most part be quite simple and leave you with a product containing little to no Gramine. Check out some threads regarding the use of Calcium Hydroxide and D-Limonene for DMT/Gramine separation.

Phalaris Brachystachys would be the greatest choice for entering into the path of Phalaris. In my experience, less plant material needs to be harvested, less seeds need to be accumulated. There are suppliers for P. Aquatica, P. Arundinacea, P. Brachystachys, P. Canariensis(sold as 'Alpiste', P. Minor, and P. Paradoxa seeds. Live clones of Phalaris Aquatica 'AQ1', P. Arundinacea 'Big Med' and 'Yugo Red', and P. Stenoptera are also available from a few suppliers. Bulk amounts are hard to come by nowadays. When you see a field of Phalaris Arundinacea gone to seed, in 30 minutes you'll have enough seeds harvested to turn the UK into a medicine meadow. Backyard experiments of course are the perfect option. Letting people pressure you about the invasive potentials of an entheogen will only prove detrimental to how deep you trek into the unknown.
Grow the grass.

Phalaris arundinacea is hardy to USDA zone 4, which includes all of the UK.
Moreover its native to the United Kingdom and has been bred by agronomists there for many decades, so people arguing against it as an 'invasive' havent done their homework. For instance, in 1959 when american agronomists were interested in breeding Phalaris for grazing purposes a plant research station in england was kind enough to send them two Phalaris aquatica X P. arundinacea hybrids they developed on an experiment farm on the english countryside. Phalaris is nothing new to england.