Two Horfield friends attempting to drive thousands of miles from Bristol to Istanbul and back in a £200 car have passed the half-way stage of their journey.

Gareth Browning and Mark Robson have reached Istanbul in their 15-year-old Honda Concerto, which was recently damaged in an accident and has an engine warning light on that no garage can diagnose.

Before setting off on their adventure, they asked sponsors to pick a mile between 0 and 4,000 when they think the car will break down and pay £5 to put their choice in a prize draw. The person with the nearest guess will win half the prize pot, with the other half going to Chicks (Country Holidays for Inner City Kids).

The charity provides disadvantaged children with a free respite break away in the countryside in Devon. The housemates, who live in Northville Road, decided to make the journey to Turkey – which they have called To The Bul And Back – simply as "something interesting to do this summer".

Mr Browning, aged 27, who works in insurance, said: "We rolled into Istanbul at midnight on Friday with the clock at 3,140 miles.

"We had a near-calamity three days back when we did 5km on some Montenegran B-road with one of the back doors wide open.

"We did wonder why the locals were shouting and screaming at us as we passed. That day later became known as The Montenegran B-road Debacle. It almost ended us."

Mr Browning said that the prize fund for the mileage sweepstake now stood at £1,100.

Mr Browning, and Mr Robson, 31, a teacher at Hanham School, have allowed themselves just three weeks to travel to Istanbul, through Belgium, Germany, Austria, Croatia, Bosnia Herzegovina, Serbia, Bulgaria and Turkey, before returning to Bristol.

To enter the fundraising sweepstake visit www.justgiving.com/tothebulandback. In the comments box include the mile you think they will break down and an enter an e-mail address so they can contact you should you win.

For more information about the work of Chicks, log on to the charity's website www.chicks.org.uk.