OP, you're kinda there. in simplistic terms, which is where it should stay, otherwise this will get dragged down into another flame-off...
When Nu-Labour got in with Tony and Gordon, they inherited a surplus. Which while not a good thing in itself, is better than inheriting a deficit, imo.
I recall that by the end of their time in the mid 90s, the Cons were as deaf and as arrogant to the wants of the people, as Labour was last year when they lost the GE. This seems to indicate that when a party is in power for too long, it all turns to poo.
"Absolute power corrupts absolutley", etc, etc. And neither the COns nor the Labs are immune to this.
Labour have now spent too much, hence the massive, record, deficit we have now.
As you have correctly observed, Labour are hopelessly addicted to borrowing and spending. Its woven into their philosophical DNA.
The cons may be no better, swinging the pendulum in the opposite direction.
Most of the "isms" have appeared to have failed. Capitalism seems to be the last man standing and while being far from perfect, is all we appear to have at this time.
So yes, Labour always spend too much, telling the people that big brother the State will wipe their backsides for them.
And the Cons probably cut too far, eventually, although current cuts are necessary. I fear though that in 8 years time, etc, if the Cons are still in number 10, then cutting will probably start to go too far, and by that time, they'll be as deaf and as arrogant...etc, etc.