The reason UK companies can't do this is because the Thatcher government carved up and privatised the national energy sector, effectively selling them to foreign governments.
Those are what used to be English energy companies doing the work, it's just that they've been sold off in packets. And the Germans and French quite wisely bought them (among others)
Before you say it, British Gas only has a small fraction of its pre-privatisation resources, and the actual plant ownership and wholesalers were split across different companies, so while the foreign companies were able to buy a slice of both the production and retail side, the UK companies were only able to get one or the other.
Additionally under pressure from the green lobby successive governments halted all domestic investment in nuclear and caved in to unfounded public health concerns (and I really do mean completely unfounded) from basically a bunch of hippies who thought nuclear plants were the same as the bomb. As such we no longer have the necessary modern infrastructure or technical knowledge to build new plants. The French and Germans however put resources into nuclear, told their respective lobbies to shut up, and got safe, clean, cheap energy out.
As such the remaining British energy companies simply don't have sufficient resources to get these contracts, while the foreign owned companies (I suppose technically now multinationals) do.