All you can do is take a front wheel off (if any fouling problems its usually at the front) and offer one up, hopefully it got a tyre on already so you can lower and move the car applying full lock both ways and to allow the suspension to settle, also make sure there is enough gap to allow for suspension compression in road undulations, not just on the straight but on cornering too, too close to the suspension leg and you have an issue, too far out and you might foul a wing on cornering or in a road dip.

There is no mention of the spigot size, but whatever it is it is, if the new (used) wheel centres are too small then you have a problem, if the centre hole is too large you can probably buy spigot adaptor rings.

The 40 stamp isn't beside the ET where i would have expected it, though its possible that 40 stamp is indeed the offset.

Make sure you have suitable wheelbolts, there are usually two types of bolt seat, tapered and rounded, you want the right sort...also drop a bolt through your existing wheels and measure how much thread protrudes on the inside, then do the same with the new wheels and compare, ideally you want a similar amount of thread going into the hub.

Presumably these are positive offsets, so the wheel's centre plane will be 7mm further from the car than your original ones if those figures are correct. That is unlikely to be critical if the new wheels and tyres are the same width BUT if the new wheels are wider then the clearance to the bodywork will be tighter still. Try them as GB suggests.

You might reasonably expect wider wheels to have less positive offset if they are wider, to preserve the clearance from suspension parts.

Spigot rings have no relevance to offset, only to the centre hole size (as you probably know, but that isn't clear in the OP).