Figleaf - lots of good advice for you from others.
Dullater as mentioned by Mrs Muddle is I believe a nice place to live. Kilsyth (next to Cumbernauld) has undergone some regeneration and has a fair amount of new housing available and is on the up also I think.
Don't be too down heartened by the house price thing there is hope without a doubt. Also the market is slowing down going into the pre-Christmas period and so there are a number of fixed price properties around at the mo which always helps.
Prices are high in BoFA/Dunblane/bits of Stirling but these areas are very concentrated and so if you are willing to live just on the egde of the super nice bits then you would I think get something quite nice for around 330K. In Stirling for example Kings Park has huge houses and is v. expensive but on the edge there is a an area of 70/80s house where you would I think get something in your price range. BoFA is split into lower/upper and in lower BoFA there are a large number of again 70/80s houses some extended/refurbished etc. which are do-able on 330K. Areas to bear in mind in the vicinity are: Cambusbarron, Cambuskenneth, Doune, Gargunnock, Bair Logie, Causewayhead, Kippen (would add about 20 mins onto a commute to Cumbernauld).
Riverside is a good bet, very central (2 mins to mainline train station) but there are very few detached house as the majority of housing is either ex-local authority (but very nice don't let that put you off) or Victorian terraces, but again some of these are super!
You might also consider Menstrie (about 10 minutes outside BoFA) with a fair amount of new builds going up at the moment - it is in another local authority (Clackmannanshire so you would need to look at school provision, in particular special needs as I have heard it ain't too hot)
Also bear in mind there is not the same pressure on schools in this area as down South so in general if you live in the local authority you would get access to the RC school and I think the unit at Riverside regardless of you address. BOFA & Dunblane and Newton PSs are the exception to this as they are full and not many placing requests are accepted.
The Gaelic Medium unit at Riverside is located in the same part of the school as the Infants and Nursery there is no isolation and secondary gaelic education is now available at Wallace HS if you wanted to continue. The mainstream classes at RS get a Gaelic lesson once a fortnight too which I am sure helps. We looked into and considered it for our DD and couldn't really find a reason to do so to be honest - academic outcomes are no higher (according to a Scottish Executive review) which is surprising given the small class size which is usually viewed as an advantage. We also were unclear as to how we as non-Gaelic speakers could support her as the work levels and intensity increased - so for exmaple I would be fine helping with her reading at 6 for example but not so confident with a geography project at 10 IYSWIM? Would probably guarantee a job with BBC Scotland when older thou' .
Right that is probably enough babbling for now. If you have questions on any specific areas in advance of your visit just shout.