Re-mortaging

ambercelery

I've had a base rate tracker mortgage for almost 3 years now and will be looking to re-mortgage at the end of January.
My mortgage was fairly small (78,000) when i took it out and I have made some frequent overpayments of around 50-100 per month. I think that when i get my annual statement, after 3 years it will be down at the 70,000 or 71,000 mark.

Can anyone offer advice on what is the best option for me?
I would prefer to pay my mortgage of asap so am not interested in low monthly payments. I would prefer to pay say £500-£600 a month to pay it off quickly than to get a low rate of £200-£300 a month over a longer term.
Also, my dad has some money that he has in his bank account that he would be happy for me to borrow for a few years i.e. 20k or so. Would i be best to get an all-in-one account, using this 20k for say 2 years to reduce the amount of the money owed. Then over than 2 years, continue to make overpayments into the account whenever possible to reduce the owed capital.
Then when i need to hand back the 20k to my dad, my mortgage will obviously increase again but i will have had some benefits or borrowing the money.

Also, the house that my mortgage is on, Is now worth in excess of 200k - approx. £210,000-£230,000?

Any help would be greatly appreciated.