In no particular order, Bala Hub 4, Skipton - Carlisle or the soon to be released Yorkshire coast route. Bala is good for shunting activities, It's mainly low speed branches but you might find yourself struggling to get past walking pace on some of the gradients with no chance of a speeding fine anyway

Skipton is excellent for a fast passenger run with a Black 5 or A3 or dragging a long freight with an 8F, The combination of route sounds such as the signalman working away when you pass the box and all the correct buildings and bridges make this route very atmospheric, It's part route and part historical document, Well worth the money. As for YCR you'll have to wait and see, It's not quite finished but the NYMR and Whitby - Scarborough sections are both a challenge to drive and great to look at. I'd say get all 3 of these routes, Then buy SVR even if it's only for the loco's and a few Bluearrow rolling stock packs. London and South East by Making tracks is excellent too, It doesn't come with any steam loco's but has the right setting for late BR steam. All good stuff and it's kept me entertained for the last year so it can't be bad.