Surely we'll be buying from Rainford Steel given their long term advertising at Goodison?
Rainham Steel, originally from Essex (founded by Mr Wm Ives, a lifelong Spurs supporter if I remember correctly) are now based at Scunthorpe to be located close to the British Steel mill which produces Beams and Columns (H and I shapes - think of girders) which is their main product range.
Depending on the actual design, Rainham Steel would almost certainly be looking to supply to any stadia work being fabricated in the UK.
But, whoever eventually supplies any steel will be greatly influenced by the actual design the structural engineers come up with.
There's lots of ways to achieve the same end results structurally and not all steel companies produce all steel products.
Large spans using tubular trusses (like LFC recent work) have been popular recently because you can suspend the roof below the exposed truss which is then out of sight from the spectators, and low maintenence compared to trusses made from steel beams, angles etc .
Think of all the exposed steelwork visible from aerial shots of Old Trafford - it's all tubes, no beams or columns like Rainham Steel supply.
Rainham wouldn't expect to get much work from that type of design. But think of Sunderland where the roof cladding is above the structure,
that would suit what they stock and what British Steel / Tata made/make at Scunthorpe.
Rainhams best chance is if the terracing is constructed from steel (like the Olympic Stadium), and not precast concrete like the terracing at Tottenhams new ground.