Dutch and British wholesale gas prices were slightly up on Wednesday in thin trading ahead of Christmas holidays across Europe, as uncertainty remains over Russian gas flows when the Ukraine gas transit deal expires at the year-end.

The benchmark front-month contract at the Dutch TTF hub was up 0.25 euros at 46.00 euros per megawatt hour, or $14.36/mmBtu, by 0947 GMT, while the day-ahead contract was up 0.69 euros at 45.92 euros/MWh.

In Britain, the day-ahead contract was 2.15 pence higher at 114.50 p per therm.

Nominations for natural gas flows into Slovakia from Ukraine on Tuesday were steady at levels seen in recent days, data from transmission system operator Eustream showed.

Nominations for flows to Austria from Slovakia were a touch below previous days but in line with levels seen a month ago, while nominations to the Czech Republic from Slovakia were in line with previous days.

Russia's Gazprom said it would send 42.4 million cubic metres of gas to Europe via Ukraine on Tuesday, up from 42.1 mcm on Monday.

EU gas storage inventories were 75.65% full, a little lower than at the same point in the last two years, but remain within a normal range overall.

"With almost half the winter season gone, stocks look fairly comfortable for the second half," said Alex Froley, senior LNG analyst at data intelligence firm ICIS, noting that the gas market winter season runs from October to March.

"However, entering next summer with slightly lower stocks than the last couple of years would require greater injections next summer."

In Britain, peak wind generation is forecast at 15.5 gigawatts on Tuesday, falling to 12.8 GW on Wednesday, Elexon data shows.

In the European carbon market, the benchmark contract was up 0.1 euro at 69.76 euros a metric ton.

(Reporting by Marwa Rashad; Editing by Jan Harvey)