The majority of imported cannabis we get is pressed and shipped from Holland or Jamaica/West Indies and is usually of a high standard because we expect it to be and won't pay for poor quality. Most of the home grown is high quality too because the successful growers have been doing it for years and want to grow better than others in their area. The only 'shwag' I've seen being sold are usually the 3g £20 bags which are pre-ground by the dealer. You'll get a lot of stalk in these 'baggies' but UK dealers usually take out the seeds before grinding. Resin is shit but continues to be a neccessary evil.

peace