Hi Lyn - welcome to the forum. Your husband is a lucky man!
The various Scalextric ranges are explained here: www.scalextric.com/uk-en/our-ranges-explained
Your main request is that three people (or more) can race at the same time. The only Scalextric sets that offers this as an out-of-the-box package are the ARC Pro digital sets. These are on the most expensive end of the Scalextric pricing spectrum and are moderately complicated to set-up - although absolutely fine for anyone who likes their gadgets. ARC Pro digital offers up to six cars running on two lanes of track, with overtaking, pit stops and an app that runs on compatible smart devices (Android and Apple phones and tablets, plus Amazon Fire tablets).
The C1388 ARC Pro Sunset Speedway set comes with three cars and three controllers, a good-sized track and a pit lane. It would fit your requirements perfectly. It is £380 here on the Scalextric website, but I have found it for £324.50 elsewhere. There is a cheaper C1404 ARC Pro Le Mans 24 hour set with two cars, two controllers, a smaller track and no pit lane. It is £250 here and around £315 elsewhere - however an extra digital car, controller, track and pit lane would cost well over £130. If the Sunset Speedway set is within your budget, that's the one to go for.
If the ARC Pro digital sets are well beyond your budget, a basic Scalextric starter set can still be a lot of fun - but only for two racers at a time. That's not the end of the world, the three would simply rotate on and off the track as people have done for sixty years with Scalextric. The cars and track can, of course, be upgraded and added to in the future.
Two starter sets that would be ideal for a grown-up Scalextric racer would be the C1383 Stock Car Challenge set or the C1372 Touring Car Battle set - each costs around £110. The plus point for the Touring Car Battle set is that it comes with a lap counter. The Stock Car Challenge set has new-and-improved controllers (but no lap counter). There's also the very nice new C1401 Jaguar I-Pace Challenge set which is due any time - it has both a lap counter and the new controllers.
Finally, both Lidl and Aldi have their own exclusive Scalextric starter sets priced at £69.99 - if you can find them. The Lidl set is called Supreme Rivals and the Aldi set is called Lamborghini Rampage. Both would make nice starter sets and both look to have a lap counter and the new controllers. Lidl and Aldi also have Micro Scalextric sets which are aimed at younger children - they are great value, but probably not suitable for your husband.
I hope that helps.
Thank you ever so much for all your help.. I have bittne the bullet and bought the one you recommended.. the ARC digital set..
I cant thank you enough, I was totally lost when I started searching them, so I appreciate your help, Your a Gem..
As for my husband being a lucky man?? Id rather look at it like this, Im going to have a quiet Christmas!!! hahahahahahaha.. He's always said he wanted one when he was a child, well, I call this his 2nd childhood!!! hahahahaha
Thank you ever so much again for everything... Im so glad I came across this forum.
Have a lovely Christmas, Im sure I will :D thank you x