Swindon's crate motors do look quite interesting. Pretty expensive compared to some DIY options - £6400 ex VAT is around what my conversion will cost in total, let alone just the powertrain parts, but it'll be lighter and you'd get some OEM support which is probably a value-add for many folks...
One advantage of that by the looks is compactness. We're lucky that our cars have loads of room where the engine was - if you were converting something old and tiny then it'll probably be pretty great.
Performance is not particularly special - 80kW is quite a lot less than something like a repurposed drivetrain from a Nissan Leaf.