margetti:
I think a Pro-ject Debut III might be the way to go - it has a built in pre-amp and a quick search on flea-bay shows a few going for under your £100 limit. I suspect it and the Onkyo won't match what your dad's system is delivering, but if you're prepared to take a bit of a gamble you might just be pleasantly surprised...
Other options to look at would be Pro-ject, NAD, and CA (Cambridge Audio) pre-amps but they will take up nearly half your budget which then limits your options on the turntable (Debut II an obvious choice).
I got into vinyl with a Pro-ject Dubut I a couple of years ago - a deck that is universally derided as being as "budget" as you can get, but it gave me enough insight of the format to get the vinyl bug - as I imagine hearing your dad's system has for you.
Yeah my dad's system does sound very nice and he doesn't even have the best of speakers to pair with it, they are sony [pair but as well now there are far better brands for audio, although sony are still very respectable. I think his amp and turntable both being marantz help it along very well.
It's funny how a modern day album (vinyl version) that i played on it sounded almost vintage and a pleasue to listen to. No doubt i love the set up i have at the moment and it does have its benefits, such as stronger bass and more clarity, but that vinyl sounded very enjoyable and different (in a good way) on my dad's set up
I will look into the Pro-ject Debut III.
Thanks for your advice.