Total Kit Car July/August 2008 rated the Vauxhall XE as one of the top ten kitcar engines:

Introduced in 1988 when GM, who had developed a good relationship with Cosworth due to their rallying exploits, asked the legendary engine company to come up with a 16v belt driven aluminium cylinder head for the Vauxhall/Opel 'Family 2' range of engines. It appeared in the Mk2 Astra GTE & produced an easy 150bhp out of the box. GM took over the head casting from early 2002 to save money & in turn used a lesser quality material, & there have been instances of these becoming porous. The earlier 'Coscast' ones are rated as being much better. The classic Fords boys are loving the XE at the minute & hundreds have been stuffed under the bonnets of Mk1 & Mk2 Escorts.

I guess their real 'kitcar heyday' was back in the mid-nineties & lots got fitted to all sorts of tackle, although Caterham Cars used loads of them too. SBD are the kings of XE tuning.